If you think your host is overselling, why not find out.

Is your host oversold? Oversoldhost.com (http://Oversoldhost.com)
Find your ip neighbors: WhosOnMyServer.com (http://WhosOnMyServer.com)

Put your site name into the search field and it will tell you how many other sites are sharing with you.

If you are interested, both scripts are for sale, and WhosOnMyServer.com is for sale with master resale rights. PM me for details.