A few years ago when we first got it, you could just log out, and then click new account, make up some bogus email, and you'd get another $4 off coupon. You didn't even have to verify the email - just type in crap@crap.com and it would work. We'd do this every time we went.
If we were feeling particularly cheap, me and my wife would both do it and check out separately to get $8 off.
They still do the $4 off for new users, but it can detect if you've already made an account or not. But man what good times.