A WebmasterWorld member posted a thread asking how critical it is to register a domain name for longer than a year. He asks, because his hosting company claimed that registering a domain name longer than one year, will improve his rankings in Google.
First, there is no conclusive evidence that the patent that Google issued that shows how a search engine can use domain registration length to determine the 'spamminess' of a site will be applied to Google results.
Second, if it did, why wouldn't spammers who can potentially make millions a month, spend an extra few hundred bucks to register a throw away domain for ten years.
Three, it is not right for a hosting or domain registration company to profit off of this, in my opinion.
Forum discussion at WebmasterWorld.
Update: It seems Google has gone on the record saying domain registration length does not impact rankings.