I find it interesting, especially on international forums where you get mixtures of cultures and ideas. when I look at Australian based forums they seem to be less interesting for me.
Is there an addictive component ????? Possibly, it may be a just another way of socialising / interacting. I use it as a distraction from work when I need to clear my head of work crap.
On a practical side it does have its uses, I have solve many problems through forums, for example I get better answers to scripting questions here then I get from some of the Automated tool suppliers. I have also got some handy tips about Open Source tools that can do the same job as many expensive commercial ones. They are also good at getting feedback on products that you may be interested in.