I don't criticise Valve's actions here (and the posts in the linked forum are largely in agreement), but there is something to be said about Valve controlling the way our games are played.
I know Valve have stated in the past that in the event Steam goes belly up, they'd ensure that people would be allowed to play the games they own, but the lack of such a system at the moment is a little worrying. As well as that, being banned and losing access to games you paid money for just isn't on: it'd be like being banned from a bar and as a result, you can never drink alcohol ever again. Well, maybe not, but still.
I'd hate if I were banned for something silly: I have nearly 200 games on Steam that probably amounts to thousands of dollars worth of content and I don't think that Valve should have the right to throw all that down the drain. Users should be banned, but they shouldn't lose what they've bought: they should lose the extra privileges that using Steam brings with it (unified update system, friends network, multiplayer gaming, bonuses, etc).
I use GOG as well as Steam, just not as majorly because their catalogue isn't as appealing as Steam's. While they don't have the same feature set as Steam, their approach for game acquisition is very sound: you download a completely DRM-free, patched executable setup file. Install it on as many computers as you want. I'm not saying that Valve needs to do exactly this, but they really should start considering what potential negative effects Steam has, considering the kind of digital distribution juggernaut it is.