Developers GSC Game World have posted the result of a public Q&A session on their forums, with some rather suprising news included.

Other than the standard news about their upcoming prequal to STALKRE, Clear Sky, and how it will keep all the support of the current STALKER engine, there is a nice little tidbit about the possibility of an MMO version of the crazed nuclear shooter.

2. Will there be S.T.A.L.K.E.R. Online?

We do not quite understand what you mean by "online". If it is the cooperative mode, then no, there will be none. Even at the time of development of the first part of the game we said that a cooperative mode is impossible, since Life Simulation would be different at each computer. Synchronizing it would be practically not doable. If you mean an MMOG, then we are seriously considering it.

It's an interesting one indeed, it is one of those games where I can really see it actually working, as STALKER's living world would only become more convincing if all of the characters were to be played by real people, from all over the world.

More when we get it, as always

Full thread here.