Same with my blog. It appears on search, but one day they decided something fishy was going on with the ads and simply terminated the service. The automated e-mail said I could appeal and the appeal resulted in a "yes, it pretty much was something fishy" automated message. No further information, just silence and a warning that they would ignore messages about this subject from that point on.
AdSense needs competition. Badly.
I don't know if this helps, but a search for adsense competition (on google no less) brought up the following:
http://www.associateprograms.com/articles/208/1/Adsense-Comp...
Which has a list of different things like adsense you could use. Out of curiousity, is there any reason why you can't switch to using these companies for advertisement? I can see how google has a complete monopoly on ad-words, but surely adsense is a free market.
They don't pay nearly as well, from what I've heard.
Google is not required to provide customer service. If "SEO" is important to you, I recommend rereading Google's terms of service and landing page quality guidelines. Google Webmaster Tools is the best way to get feedback on your particular site, though I don't recommend using it on every site in your network.
Yeah, I'll just take my business elsewhere... oh wait.
Since we're focused on Google, logically the best strategic decision is to accept that you can't change the terrain on the battlefield, and adapt your strategy accordingly.
If Google has an achilles heel it's definitely lack of customer service.