http://www.seroundtable.com/google-old-penalties-expired-dom...
It seems like old bad links can hurt an expired domains rankings.
"On expired domains, Matt said Google tries to reset pagerank/links for all expired domains to zero when they are registered by someone new. They don’t try to penalize the expired domain, but they also don’t want to give credit for the previous owner’s links."
http://www.seo.com/blog/conferences/matt-cutts-does-domain-r...
People used to snatch up expired domains and use the internet archives to put back up the same content and than slowly add links to their sites...
Because of this spam, Google just ignores links to a domain that expired that are from before it went live if the new registrant is a different person I presume but don't know.