You're speaking from the point of view of an owner of a very small site, though. Your stats:

It's not nonsense, it's just that your site is small and your traffic (by comparison) is very low. You can't really expect to get a lot of revenue with only 200 members and 20k views. For bigger, busier sites, it's certainly worth it. I do agree that it's not worth running on low traffic sites - the payout isn't worth putting ads on your site when you're trying to build a memberbase. For big sites however, it does pay pretty well. I've broken $300/mo and there are guys out there who've done that much in a single day off of Adsense. It's all about traffic, and figuring out what ad placements work best on your site.

You can't just toss up a board and throw ads up and expect good results. You really have to work at it to find out what ad locations and formations work best on your content, pay close attention to your CTR and constantly optimize to make the most of it.

Edit: I'm not sure if you've already taken it down, but I'm on your site as a guest right now and I see no ads at all on your forumhome, and only a single text unit at the very bottom of your postbit. The best performing spots have historically been the upper/upper-left areas. Nobody's clicking your ads because even guests usually don't see them.