What happens if you clear your cookies?
http://stackoverflow.com/users/account-recovery (this is linked from /users/login)
It does require that you provided a valid e-mail address at some point, which we don't require.
If you do provide one, it lets you recover your cookie based account is all.
The "account" is as throw away as you want it to be, basically.
Looking at the code, we do require something that looks like an e-mail, for recovery purposes (I assume, that code predates me by a bit). It is not, however, verified.
You can get the lion's share of a Stack Exchange's utility without registering, and this is quite intentional.
(a) the end user has lost something invisible that they didn't even know they had
(b) the method of recovering the invisible token is to go to what is probably the last place they are going to look
a + b = full retard
// and you should never go full retard