From the Steam site:
"The Steam client application's files must be updated to allow for the use of Offline Mode. If your game's status is "100% - Ready" but you receive the message "This game cannot be started in Offline Mode" when attempting to play offline, the Steam client application's files need to be updated."

That's the Steam client files, not the game files (there's a difference). You said the game needed to be updated before it can run in offline mode, which is not true. You can actually tell Steam to not update your games at all and they will continue to work, regardless of whether you use offline or online modes.
When Steam is run in offline mode for a while (not sure of the exact time frame), it throws that message automatically, even if there actually is no update to be had. Its just a way to force you to occasionally check for Steam updates (a DRM thing, I'm sure).

Yeah, I think I mixed the forced auto-updates in with that bit, hehe. My bad. But yeah, sounds like definite DRM to me, which is unfortunate, and one of the reasons I choose not to buy from Steam..

You can't say "piracy has forced increasingly intrusive DRM upon us" and not be biased. It's been proven that not a single DRM method ever has stopped piracy. It doesn't even slow it down. Piracy hasn't forced anything. If anything has spurred on the excessive DRM, it's the second hand market(in other words, greed). Those limited activations were more aimed at killing off your ability to resell games you legally own and have a legal right to resell. DRM is purely about greed. Of course, piracy is purely about greed too.
Spore and Mass Effect set new records for completely destroying the claim that DRM is even necessary at all. I can't even imagine that most of the people who downloaded Spore actually played it. I could tell from the previews alone that the hype and the actual product were two entirely different things. Spore was more like a really fancy character creator than some kind of in depth evolution simulation as it was hyped to be. I suppose I could play it to confirm this but everyone I've talked to who's played it basically confirmed this for me and I'd rather not waste my time or money on it. Mass Effect was another over hyped and over pirated game, though not to the extent that Spore was. The point is, both had overly restrictive DRM, both had problems running because of that DRM, both had their DRM nerfed by a patch shortly after release but by then the damage had been done because both were being pirated en masse from day one.
So please, tell me how DRM helped either of those games even a little bit.
I think even the idiots who can't figure out how to put a disc in their "cup holder" have managed to figure out how to use torrents. After all, download numbers don't lie and I just can't imagine that not one of those people downloading fall into the category of "casual" user. If you're smart enough to figure out how to "burn" a disc then you're smart enough to click a torrent link. I know, it's really hard for some people to figure out how to use an automatic program to copy a disc but those same people who can't figure out how to copy a disc really can figure out how to use a browser, even if they can't pronounce the word browser. I work in tech support, so I know these things from personal experience. This isn't some he said/she said random statistic made up on the spur of the moment. I've seen these people face to face and had to teach them how to use a "burner" since the process of adding a few files and hitting Next a few times is too much for them. So, there goes the theory that DRM stops casual pirates.
Game companies that use DRM are either greedy or are being given the choice to publish with DRM or not publish at all because of greedy publishers. I suppose it's possible some game companies are being conned into believing that DRM actually stops piracy but you'd have to be rather gullible to fall for that. It's really a relief to me to see a company that actually has enough sense to not buy into it and to drop the DRM. Yes, I know GoG isn't the only company to support DRM free gaming. I have love for all the companies that try their best to avoid DRM and a great deal of respect for those to completely buck the trend and go completely DRM free. I'm really hoping for a great deal of success to those who are brave enough to do what everyone else says is wrong by going DRM free. It's not just in the best interest of consumers for DRM to go the way of the dinosaur. It's in the best interest of all involved, except maybe pirates. Without DRM, pirates would lose their purpose and any moral leg to stand on. This would give me a great deal of pleasure since it would mean that society has finally chosen to move in the right direction again. For a long time now, one of the keys to a successful business has been trust but a lot of people seem to forget this and the trust has been going further and further away. It's time to bring back some of that trust and hopefully with it some respect too.
As for the actual topic of this thread, I think it really would be more effective for people to comment on games and the effects of the DRM in that game rather than just list games and the DRM they use since there's already plenty of websites you can find lists like that on. Personally, I avoid any game with abusive DRM like the plague so I don't have a lot of DRM stories to tell. I have had issues with it in the past but my memory is terrible and I've already forgotten about them. Well, I suppose I've forgotten about those more intentionally than simply because of having a poor memory. The reason I haven't had DRM problems recently is because all of the games I've bought either didn't require online activation or were online games. I can say that some of the CD checks some games impose are annoyingly long and add a good 2 minutes or more to the start time for a game but even some of those games patched out their DRM.

have you seen any working rips of Left 4 Dead? how about Team Fortress 2?
I'd say Steam and Multiplayer games are effective forces for stopping piracy of Valve titles.
Mister Jumpy.

Just a minor quibble here, but Mass Effect didn't have its DRM nerfed in a patch. It's still exactly the same as it was when released. There's a rumor of a revoke tool in the upcoming 1.02 patch though, but as things stand the DRM is currently unchanged from release day.

I'm rolling my eyes very hard at you. :P

There has been a working rip of Left4Dead since within a week or two of release. I don't remember how long it took but Team Fortress 2 has been available for a long time now. Don't expect to play on Steam servers though.
You probably wont believe me but there's even pirated versions of WoW. You wont be able to play it on an official server but it's still playable on private servers.
I'm not trying to promote piracy. I'm just pointing out how effective it is and, in contrast, how ineffective DRM is.
@Coelocanth
I don't really keep up 100% on the details of what happens to games I don't play. It's entirely possible I'd only heard it was going to be nerfed and never actually confirmed that it happened.
@chautemoc
I'm sure that "backup" collection you downloaded is entirely for the benefit of all man kind. o_O

Yeah, I've been following that one since I'm a huge fan of BioWare's games, but refused to buy MEPC with that kind of DRM. I was pretty excited to see they put it up on Steam without the DRM attached, but I'm no fan of Steam either. So I'm hoping at some point they'll put out another edition of MEPC with a different copy protection system. A pipe dream, I know. But maybe once the trilogy is completed there will be a 'Gold' version (or something like it) with all three games and the additional content and they'll get their heads straight and not put this asinine DRM on it.
Meh, a man can dream...

To be fair he said a "single" method of DRM. That appears to be two things. That is, you know, if I wanted to nitpick.