I have a handful of (content unrelated) sites with decent PRs and I'm considering hosting them all on the same server. I've heard that if you do this, internal linking between two seperate domains on that server may be seen as less "valid" by Google in PageRank terms (since you obviously own both of the sites as they share an IP address).
Anyone have any experience in this? I'd love to save some hosting cash by consolidating, but not at the expense of losing the ability to link my sites together powerfully.
Google is very clear that they do not penalize sites for being on the same IP address or server.
Matt Cutts of Google answers the question very directly via Google Video.
Another direct quote, from seroundtable.com:
If you're really worried about the overlapping IP addresses, just get a second VPS - the additional ~$30 per month sounds like a minimal cost to have. Or add a second IP address to your VPS for $2 a month.
On the other hand, shared hosting may utilize the same IP address for multiple domains that aren't owned by the same person - so I don't think this is as big an issue as you do.
However, I am not an SEO professional.