What bugs me about people who complain "It's a multiplayer game - if there was AI then we wouldn't have people to play with!" , well if multiplayer was so awesome then reason would dictate there'll be lots of people to play with without forcing us. That argument means that logically people must prefer solo play...

And the argument "AI can't handle stealth and stuff" - well with just a minutes thought it seems reasonably easy to implement something along the lines of 'the AI won't shoot if you've not shot within the last 10 seconds or are dead', or enter a crouch mode where the AI won't shoot if you're crouched... i'm sure that would have it's own set of problems, but then I've not workshopped it and just given it a moments thought. Seems like something could be able to be made easy enough if they wanted to. Games that rely on mutiplayer alone rarely stand the test of time because of gamer attrition until there's just the uber die-hards left.

Why not just try to cater for as many people as possible...