This is a very serious problem. I'm glad I purposefully chose to NOT use IRC, and not try MUD/MOO games 10 years ago when I was getting into the Internet. I knew that I'd become addicted to them.
For the same reason I've never played Quake. I was addicted to WarBirds for a while, and that was a serious problem for me. One way to avoid these things is to make sure your computers aren't game-worthy. It's happened to turn out that way for me, not that I'm proud of that!