I am registered but don't always log on just to view what's going on but I do have to log in to post a reply or check the politics forum.
Prior to registering, I would just visit occasionally maybe once/twice a month, since getting "packaged off" last year and now being a stay at home dad for my girls I have more time and something to contribute - on occasion.
You have to remember the wide scope of our members, some are young and some are old, some work full-time, some work part-time, some like me don't work at all and for many of us this is just not a facebook/twitter world.
....... And just think of all the time zones we cover, right now its 3:45am.