I do that but only with recruiters from LinkedIn. It's hilarious when they get really upset and either call to curse at me or send a bunch of angry emails. Emails of course just get forwarded to their main contact. That'll teach them.
The bad spam recruiters seem to have found GitHub in the last few weeks.
eg not the "normal" recruiters who have a clue, but the ones who just email everything through regardless "just in case".
I had a lengthy discussion with one of the managing directors (Nick Rapley) of such an organisation ("RBW Consulting LLP" here in the UK) recently. He goes out of his way to defend their approach, as if the anti-spam laws don't apply to his line of business. Just because some small % of people might actually be convinced to say Yes.
(that is literally the same justification every other spammer uses)
Ironically... he told me to stop wasting his time. Like... hello, pot calling kettle black. :/