A dedicated IP is needed for some cases. Setting up your own Domain Name Server. (i.e. NS1.yoursite.com, NS2.yoursite.com). However, since we provide you with our DNS servers, you don't need to have your own.
Using your own Private SSL Certificate. This applies only if you need to use your own SSL certificate. If you are using the shared SSL certificate, you do not need a dedicated IP.
Anonymous FTP
There is a common misconception that you might get penalized by a search engine if someone sharing your IP is spamming. 95% of web hosting services are on IP sharing environment and it is unwise to penalized a site base on IP. Instead, they will based anything on domain name (strictly not the IP). So it is definitely search-engine-safe to host a site on a shared IP environment.