[grawprog]

Hmmm I wonder if using a second browser, maybe based on a different renderer, in incognito with a different user-agent set up would be enough or if it would still get enough info. At that point it would still have your outgoing ip address at least is there anything else they could still match to a signed in session? I guess you could also route all traffic in the unsigned in session through a VPN too.

[antsar]

Quite a few variables are used to track you, many of which do not change between different browsers.

Try this: https://panopticlick.eff.org/

Specifically, check out the "fingerprinting" details.