Matt Cutts of google said that google does not penalise domains not hosted at their own dedicated IP here: http://www.mattcutts.com/blog/myth-busting-virtual-hosts-vs-dedicated-ip-addresses/
If you are using shared hosting, there will still be many sites at the same IP address even if you use three separate shared hosting accounts.
Matt Cutts's blog is worth following to keep up to date with developments at google from a site owner's perspective - and it is running on WordPress even though google owns blogger.