Removal of regional restrictions.
Whenever a game is released in some censored version here (in Germany), that will be the ONLY version that can be purchased via Steam. Even if the uncensored version is neither banned nor indexed (like in Bioshock's case). I can legally buy these games in any import retail store, order them from foreign Amazons etc., but Steam won't let me buy them regardless. Technically even banned and indexed games can be legally purchased here as well (certain conditions apply) but the situation is a little tricky since they are not allowed to be advertised in any way (as far as I know they cannot even be put in a store shelf), and these games simply being displayed on Steam could be seen as advertisement.
The funny thing is though, that apparently some games, like [Prototype], can be bought with a German IP despite being indexed.
As for foreign retail copies: Sometimes you can activate them with a German IP and get the foreign version, sometimes you can't. Sometimes you get the local version if you do. It is apparently up the publisher/developer what happens in these cases, but it creates an atmosphere of great uncertainty with new releases.
It is probably against the law for Steam to bar German players from activating their (usually legally obtained) foreign copies, but it's not like they care.
Some older games do not even display proper information on wether or not they are censored, although I guess I should be glad that Steam does provide that information at all (PSN certainly doesn't).
I also heard that apparently Swiss players can only get the censored and German-language-only version of Wolfenstein:TNO via Steam as well, which is beyond ridiculous.
I kind of understand that Steam is often just trying to comply with publishers as well as generally trying to be on the extra safe side of the local laws, but it is really annoying at times. Especially since they don't seem to care about a lot of other things that they would be legally required to do, like providing proper refund options, or verifying the age of its users[footnote]PSN, for example, actually does this. In order to get money onto your PSN account you either need a credit card (which requires you to be 18 here as far as I know), or you need to buy a PSN wallet card, which are only sold to people older than 18. That way the user's age is always verified in some way. This also means that demos or free games with an age rating of 16 or higher are either not available in the German PSN store or cost money.[/footnote].
The only way to safely buy foreign products via Steam would be to somehow change my IP, but that would be against Steam's rules and could get me banned, a risk I am really not willing to take, even if an actual ban is highly unlikely.