Google has a few different penalties. Most penalties result in your site dropping in rank but they still remain in the index. The ultimate penalty is when your site is dropped from the index and that can be permanent or at least last for years (speaking from personal experience). If you go to Google.com a few weeks in a row and search using your site's url and it doesn't show up in the first page of search results (and it used to) there is a good chance you have achieved the ultimate penalty.
*Note: Be careful if you are searching from a toolbar instead of directly from Google.com as you may be taken directly to your website and you may think that means you are listed in Google - it doesn't.
_________________________
For the non-do-it-yourselfer! Proven effective managed
Promotional System / Websites for Realtors - Some areas available that offer some pre-existing top 10 search engine positions!
18 years as a practitioner of SEO. Visit my
Realtor websites blog for maintaining a successful online presence.