According to this post on the 3D Realms forums, the Triton digital distribution service that was used for the online release of Prey is shutting down, just several months after the release of that game. However, it looks like people who bought the game from Triton won't be totally screwed as Triton's Royal O'Brien made this post later in the thread (thanks FiringSquad) mentioning that he's working on a patch that will remove the game's dependency on Triton.

I am making sure I have permission to get this pach out first so that I dont run into legal issues. When some of the dust settles, I should be able to give a better picture. From my perspective on digital distribution, this is essential that the patch be released so that no one is left out in the cold and it doesnt get a mark against it. I'm working with the guys at 3DR and HH for Prey. If you just purchased it and you didnt get a CD key, or have comments / flames (or not), drop me a line at [ thebox a.t. obwando.com ] and I will do my best to get things resolved as I move forward on my next project. That is my personal email box, and not a company address.