The idea of setting a fee for contacting you exists over at 21.co -- you can set up an inbox and charge $1, $5, $20, or $100 per message that people send (the assumption being that you agree to read & respond to all messages). It seems cool for people in high demand - there are a few CEO types who set it at $100 to filter out most of the crap, then donate the funds to charity so it isn't scummy.