AvPNews.com has posted an edited chat log from the David Stalker chat which was held July 30 on Mplayer.com. David is the producer for Fox Interactive's Aliens versus Predator and the chat answers questions about why an AvP level editor has not been released ("the tools used are not suitable for public release"), and much more, including this about something I've wondered about myself, Alien co-op:

Dave Stalker: Honestly, Alien coop is tricky because of AI issues but it's something that we may investigate in the future expansions that we will be doing.