There is a webmaster at DigitalPoint Forums who is convinced that Google has penalized all his sites that were verified in his Google Webmaster Tools account.
This webmaster claimed his sites are clean and he complies with Google's terms of service. But they were all penalized soon after adding them to the same Google Webmaster Tools account. I find this all hard to believe.
It is possible that they were linking together in a weird fashion, but I am not sure - since I don't know the site's URLs. It is possible they were violating the terms of service. It is possible he accidently excluded the pages in his robots.txt. It is possible he had server issues. It is possible he spammed the heck out of his pages. I don't know.
But it is common sense, if you are doing anything borderline with Google. Please don't tie those sites to others via Webmaster Tools. Even more so, why are you verifying a site that is borderline spam with Google in the first place? To me, that seems like you are testing Google, teasing them to ban you. If that is what you like, then go for it.
Do you think Google does site wide webmaster tools account penalties? I guess this is an obvious question. Google sees spam, a human looks at it, it notices the site is verified in webmaster tools, then looks at all the other sites by the same account holder and sees the same type of spam on those sites. The Googler clicks the big red blinking button and bam - goodbye sites.
Forum discussion at DigitalPoint Forums.