all (well virtually all) non-dedicated hosts will be like that. and my guess would be that MOST sites on the web are using virtual hosting. you don't get penalized solely for it... ... however, if you're hosting multiple sites on the same IP and they crosslink (link back and forth between sites), the value passed may be decreased (or nullified completely in some cases) but no one really knows for sure.
The ability is there to do it; if they want to let you have the ips. Cpanel is very versatile; and you can do most anything with it.
For this reason we have been separating sites to different IP's. Also on a virtual host so we are actually with two different companies which spreads risk too albeit a bit more hassle. But it has turned out just fine. Only one of our sites has already been caught by G's 'affiliation' rule and seems to be hooked up in the SERPs with the site we moved. It hasn't dropped this affiliation marker since the move, even now it's on a completely different IP. The other two hower seem to be regarded as completely seperate still. And probably will stay seperated because of the separate IPs. If they won't give it to you, go with someone else. Spread your assets, don't rely on one guy/company.
We were in three places, UK and US, now two spread over 8 hosts, I will take the safe option I think for sure.
If you are going to do a lot of cross-linking then it is better you get different IPs for the domains. But I really do not think that people get penalized for using a virtual hosting service.
There are masses of examples of sites disappearing from the SERPS for linking between sites on same IP. I know of many who did so inadvertently, and are now waiting for their sites to have the penalty removed.
The safest way really is to host across multiple IPs. Link farming on same IP is just plain bad news.