I would like to think that there are some people who enjoy a sense of learning and achievement. IE you get more information, you know more than the next guy and you can lord it over them when you get together for post work drinks. The achievement part comes in when you get more online status. Either your hit rate is higher, your posts are more, your manna is higher or you just get to darn well say your piece. In any event you get a sense of improvement which is almost like cleaning out your workshop or garage. Only its less messy and much less exhausting.

Also computers have the "pretty colours and pictures" thing going for them. Now I know that we are hardwired to focus on those. So on another level we're hooked.