jbayabas - 5:36 am on Nov 6, 2012 (gmt 0)
Funny, I thought Google was the only one who knew for certain the specific reason they banned an account.
Top 3 reasons why an account is disabled:
1. Invalid activity
2. Make pages specifically to display ads or minimal content
3. Multiple copyright violation
Number one is the most common -- 90% of the time. I'm sure the OP did not receive an email because he was already directed to Invalid Activity support page when logging in.