Is a dedicated IP address necessary?
For general SEO purposes a dedicated IP is not necessary. There is no advantage to having your site hosted on a separate IP address. To read a post from Google Fellow Matt Cutts Click Here. For those you you who do not know who Matt Cutts is, click here. There are a couple reasons you may want to have yous site on it’s own IP address.
If you need a secure server https protocol for e-Commerce.
If a site on the same IP as you is blacklisted you may want a dedicated IP address.