you are mistaken. This was the case until about 2008 or so... here is a quote from matt cutts.
"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...