Big G already notifies select webmasters of issues that lead to penalization in their search engine through their Sitemaps program. Webmasters using obvious spammy techniques will not be notified under their Sitemap program.
In addition to using the Google Sitemaps tool to see if a site’s been banned from Big G, there’s a free software tool available that runs right from your desktop. In addition to checking whether a site is cached with the “site:” command, it also checks sites that link to you to determine if they have been banned as well.