I can only speak from my experience, but I wouldn't suggest it. I put them on my blog about a year ago. I got up to about $14 and then they cancelled me because of "suspicious clicks." I couldn't get any information more than that, so I really don't know what happened. I asked for a review and was denied a second time. I wasn't getting much traffic on my blog, so I haven't posted in a while. I'm hoping to get back into the swing of things after Christmas. I'd love to be able to make a little extra cash from it, so I'm excited to see what others have to say about their ads.
I've been doing it for a couple of years. I don't have a tremendous amount of traffic, but I did already get a $100 check mailed to me last year. I'm up to about $70 so far this year. So, I recommend it only because it's free, there's not much to do as far as upkeep, and every now and then they send you $100.
Adsense is contextual advertising. That means that it looks at the content of your page and chooses ads related to your content. Some content is more valuable than others. So, the amount of money you'll earn depends upon the type of content you have. Here are the keywords with the highest cost per click: http://www.spyfu.com/TopList.aspx?listId=3
The only place I know of that had it was a forum I was a mod on. And he, too, got cancelled because of 'suspicious clicks'. I'm also not really a huge fan of ads on websites of any sort. Although I understand that sometimes it is necessary to support the blog/forum, nothing drives me as crazy as going to a website and getting popups or those on-screen ads you have to close before you can read anything. We added a webring to our forum, also so that it would support us. And for a little while there, it was redirecting us to somewhere else, and we'd have to click a link for our own forum.. I was NOT impressed. Although the webring fixed the problem, they never admitted they had done it (and were quite rude about it honestly). My co-admin now rents out ad space on our page for $10 a month, and that does ok. He does a lot of footwork to make it go though.
I've had it for a couple years now and make about $200+ a month. I've never had an issue with suspicious clicks. In fact I'm just about ready to buy my DS13 a new bedroom set with the adsense money I've been saving since August.
