Analyzing the move to require Steam for X3 games is a complicated matter. There so many aspects to it. I hope to keep it short (heh, who am I fooling).
Steam is many things in one:
- it is an online shop
it is a digital distribution platform with automated patch distribution
it is a heavyweight client that can connect players in multiplayer, community features, etc
it is an always online DRM (offline mode offers temporary breaks from that, but it's still required for _every_ install of the game, can't install from backups without Steam connection)
it is an API to the features above
The DRM problem
In their FAQ Egosoft said that the online shop, digital distribution platform and API were the main reasons to go this way, it provided a larger market and an easier to use patch system. The larger market argument I don't buy simply because you can get even larger market by offering Steam alongside other options, Amazon Game Downloads for example is a pretty popular (DRM agnostic) optionn, by offering the product just on Steam they are actually limiting themselves to that market so it makes no sense to say this is done to get access to a larger market. For the patch system, as a software engineer, I can understand their point. I'm only sad that it's so costly for them to produce standalone patches so they have to decide on using Steam just because of that.
If Steam were to keep just to the first few points (be an online game shop and distribution platform) while not requiring any DRM it would be better (but not perfect). As I understand some old games on Steam are already this way, they can run from their executable which doesn't run the Steam client. That's one good step. Another would be to make it possible to make local backups of the game that allow one to install it without Steam interference. At that point, Steam may be used as a convenience and for the initial activation/download, just like Amazon Game Downloads (which is just a digital distribution platform, they actually recommend that you backup your downloaded install kit that can be used for installations without involving Amazon).
Egosoft has said that if Valve goes bankrupt they will release a Steam free executable, of course that assumes that Egosoft hasn't gone bankrupt in the meantime... Also, with bankruptcy things are not black or white. The bankruptcy judge has almost unlimited power in how to manage the company's assets to pay its debtors. There was a recent news how a bankruptcy judge allowed to sell the private user information that wasn't allowed to sell according to the bankrupt company TOS, effectively changing the contract under which users gave their information in the first place. So don't be so quick to point out easy solutions (ex. all Steam games become available without DRM, yeah right) or point at existing (pre-bankrupt) TOS, promises, etc, they have no value in the case of bankruptcy.
Don't keep all your eggs in the same basket or Steam may stop access to a game for any kind of violation of their hefty TOS while playing some other game on the same account.
Did you know that you are in violation of the Steam TOS if you play 2 different games at the same time, registered with the same Steam account, and thus may lose access to all your game library purchased on the same Steam account? One way to play games using the same Steam account is to (ab)use offline mode. But since it's a violation of their TOS, you're risking your game library. Notice that the same thing would be perfectly allowed with DRM free or normal disc check DRM. It's only an issue raised by Steam DRM and their TOS.
You may say that these things don't happen, I will say it's enough if it ever happens to you. I know at least 2 coworkers that had problems with their Steam account which were very painfully (as in weeks) resolved by Valve. In all that time they didn't have access to any of their _other_ games.
Solution: just create a separate Steam account for every game you really care about. This way, you should not lose access to them all because you violated some fine print in a large TOS while playing some single player game.
Impact.
It's hard to say what the impact will be, in terms of sales. Some people have said that those who don't like Steam are a minority. To the general gaming population, definitely so. To the general Steam gaming population, obviously so (most of these people would not be on Steam). To the Egosoft existing customers... not so obvious, I would say. This is not obvious first because Egosoft's existing customers market is different from the general gaming population and second because these "hardcore" gamers that everyone likes to marginalize actually matter more (in terms of money, see below).
Quick question: how many people here have bought one X game multiple times because of a combination of factors like: oh, it has all the recent patches in plus it's DRM free and I get a cozy feeling for supporting this cool European small developer that releases DRM free games and free patches 3 years after the game was released.
So Egosoft got a lot more money from me (and as far as I can tell, plenty of others on this forum) because it was convenient to get a bulk of updates integrated in the latest DVD release and because it was DRM free than if they were to release on Steam. If they were to release on Steam, even if we assume that I would buy it once, I would have no reason to buy the game again, I'm getting all the patches from Steam anyways, plus they force me to use this one online distributor which is not nice so I feel less good about them. So, I will stop advertising Egosoft about how cool they are on the gaming lists and forums where DRM issues or space simulation games are being discussed.
So, when you lose one such customer you are not losing _one_ sale, you are losing a couple of direct sales plus all indirect sales as these people spread the word. By that argument these people matter more.
It's been said that DRM critics are very vocal, when compared to the general population, that may be true, but that also means they are vocal in general. These same vocal critics of every DRM are vocal supporters of DRM free games and companies, thus those companies get word by mouth support from these vocal folks.
Conclusion.
Will I buy X Rebirth? If it's Steam only, maybe, when it will be a sale for <$5 so that at least I won't feel like I'm losing money if/when I'll lose access to the game for whatever reason. There are way too many good DRM-free games (mostly because of they are old and patches had removed DRM) to care so much about X: Rebirth to buy into the restrictive Steamworks DRM for any serious money.