The site below runs a test on what it calls a "browser fingerprint" on your computer based on several different factors - NOT including cookies - and tells you how "unique" they estimate you are compared to other connections. Is it possible that eBay might be using something like this on top of everything else we know they look at?
That's a great site. I knew that even free IP trace sites display browser info, but they don't say how unique your settings are.
I'm not sure if the stat are correct, but it says my browser is 1 /800,000 ratio. When I turn Java off it goes down to 1/36,000. I'm not sure how this compares to other people?
Well, it can only measure how "unique" you are in regards to the pool of users they've already tested.. so in theory it will get more accurate the more people take the test later on. Only just over 800,000 have done it so far but it still gives you a good idea of what kind of things can change your fingerprint in general.
Mine was actually completely unique among their sample size. Apparently because of all the plugins I'm using.
"browser fingerprint" test 
