I'd like clarification on that as well as I heard a similar "rumor" so launched my newest domain on another server, just in case.
I've also heard that it's fine as long as they don't all link to one another. I have about 20-30 sites on the same server but only a few have links to others on that same server. Can anyone clarify?
No harm, just reduced effectiveness of any links between the sites. There's always a chance of sites on the server in question being banned and making the neighbourhood a bad one.
As long as they are not all interlinked. I have many sites on the same server doing very well. No problems.