Its useless because if two website are from same IP address then there is no benefit to build a link on both websites.
Hi Dear frnd "myfastrupee" Yes Same IP is also one the factor of get the Page Rank. When you are doing Submission, any type of Submission like Article Submission, Directory Submission, Social Bookmarking Submission, Classified Submission So all the directory should be in different IP. It will help to your website crease in SERP.
Creating a website hosted under the same IP will obviously affect your ranking as well as the ability to communicate with certain hosts. Like for instance, in the email, if someone is using an email that shared the same IP will be blocked for spamming, then, your email will eventually be disabled as it carries the same weight with the blocked email. Thus, it is not recommended to share the same IP. Instead, a dedicated IP is the best to have.