Detect multiple accounts by way of a cookie?

[TJFweb]

Hi,

I've been using the ipinfo extended info hack which can tell you which users have the same IP. It's been good for tracking down people with multiple accounts but it obviously doesn't work if they're on a dynamic IP or if they use a proxy server to change their IP.

I was just wondering if it would be possible to have a hack which writes a small cookie (independent of the standard vB cookie) that writes their userid (or something more effective) so that it can be used to determine if they use multiple accounts.

Sure it won't work if they clear their cookies or use a different browser, but it's an extra layer of defence against those inscrutible users.

Thanks.