I duno how they go on accepting people into google adsense, the 1st time they rejected me but when I had fixed up my site they accepted me in less than a few hours, although there is some requirements found here
https://www.google.com/adsense/faq
I think joining google adsense is a must for every webmaster, I dont make much on my site of them but its paid for my hosting and domain which is not bad.
I had never seen google adsense down, so this must be the first for me