This scares me, because you don't have to be very "smart" to remove everything after the + (or -, for us qmail users). Then your real address is exposed.

Much better to use SOMETERMYOUFILTEROUT@yourdomain.com, or throwaway-account@mailinator.com. (I love how many sites block mailinator, but don't block its other 8 billion domain names. Wunderbar.)

Don't you know that having a plus sign in your email breaks half of the websites' regex.

    "There is an invalid character in your email address,
    please try again."

I've also seen some website "clever" enough to remove the + sign when sending some of their emails...