Buying old domains for SEO benefit

[Linkster]

oldbrad - in the case of a SE like Google who is an accredited registrar, they have access to the real backend whois database where each "owner" is assigned an ICANN registrant number ID - and unless that changes it would be assumed to be the same person.
For an actual change in the database to a new owner the value of a domain is zeroed out when it changes hands in Googles eyes - however there is a residual benefit if there are old links to the domain if the target text of the old links matches the new content - though currently (and for the last 2 years) Google has been experimenting with ways to negate the value of those links as well - thats where the old term of "sandbox" came from - it was actually a dampening factor that was added to recently transferred domains