From BoingBoing comes a handy-dandy checklist of flaws in anti-spam "solutions."
Your idea will not work. Here is why it won't work. (One or more of the following may apply to your particular idea, and it may have other flaws which used to vary from state to state before a bad federal law was passed.)
( ) Spammers can easily use it to harvest email addresses
( ) Mailing lists and other legitimate email uses would be affected
( ) No one will be able to find the guy or collect the money
( ) It is defenseless against brute force attacks
( ) It will stop spam for two weeks and then we'll be stuck with it
Exercise for the reader: how many of the national spam solutions in our ongoing survey of Spam Laws Worldwide turn out to be "solutions" when measured against the checklist?