My 2 copper pieces:
If your games become Steam only, you will lose me as a customer permanently. I don't rent games. Either the game is mine to play/install/mod/delete/whatever from now till the end of time, barring failure of my backups, or I am not paying for it.
I did buy one Steam game by mistake - Skyrim. I bought it from a distributor and there was no clear label informing me that the game was Steam only or I wouldn't have purchased it. I purchased every single Elder Scrolls game and several in Gold or Ultimate versions... Skyrim is the last they'll see of my money and patronage for as long as they keep insisting on Steam. I purchased every single Civilization game, sometimes several times (lost CDs, different versions, impatience). I haven't purchased Civilization V and never will, for as long as it remains Steam only.
I bought up a whole pile of CRPGs - Baldur's Gate, Baldur's Gate II, their expansions, basically the whole series up until Bioware started using Steam. Again, that's that for me, no more Bioware purchases.
And just so it is clear - I am not rabidly against paying money for regular access to a game server for games where this is a component of play. I've been playing Eve Online for almost a decade now and will likely continue. If a game is online only then I don't mind centralized control. If a game has an offline component, such as a single player experience, then I won't tolerate any loss of control over the game if I pay money for it.
On the point of popularity of Valve and their promises to unlock access to games in case of bankruptcy or sale, I can only point to Direct2Drive -> GameFly transformation. I had a number of games purchased from Direct2Drive which GameFly doesn't support so those games are lost to me. Valve may go the same way at one point and there's nothing any of you can do to prevent it or influence it. I've learned from personal bitter experience that *everyone* that can screw you over when money is involved, will do so without blinking. Unless you have some leverage over them, that is. And I have no leverage over large companies. What, are they supposed to shake in their boots over my empty threat to sue? Personal promises from random people are worthless without having the ability to enforce those promises. Does anyone here have a personal relationship with head of Valve they can lean on? Perhaps a private army they can send after him? Several politicians in your pocket? A pile of money Scrooge McDuck would be proud of to pay an army of attack lawyers? No? None of the above? Well, then, Valve's promises are worthless to you.
If Stardock wants to distribute over Steam, I don't care as long as you also offer a non-Steam version, or more precisely, a version which is under my control (as a customer) if I purchase it. Any form of third-party software, phone-home, Internet-required crap is unacceptable to me.