nicidivine - 1:59 am on Jan 27, 2006 (gmt 0)

Google will do a related check based on anything they can idenity you with that account.

Mac address of any computer that has logged into the two acounts
ip address of any computer that has logged into the two accounts
cookie on any of the computers used to log into the accounts
physical address of checks
current/previous ownership of domain names.
mail servers where emails are sent from
ip addres of sites

I expect there is an endless list of things google can check to see if you have something to do with the other account.

I'm pretty sure, their check list is tight.