>I don't mind in principle if you play spammers dirty tricks - I am tired of them myself. However, I suggest you bear in mind two points: 1) Justified or not, they might still sue you for this sort of tricks. 2) Make sure the phone number really belongs to a spammer; you might easily be playing tricks on some legitimate business.

Frankly, I don't see any reason to be gentle with advertising techniques which try to steal your time. Anyone shouting at the bazaar is advertising their ware, but that doesn't incur any trouble to the passer-by; one can just walk by. However, sending unsolicited email takes a few seconds from the recipient - at least to look at it and delete the message. And that's the best case; in many countries you don't have flat rates for phone and web, you pay both by the minutes, so spam actually incurs a cost for the recipient. The only worse case is spamming via fax - wasting the recipient's paper and toner.

I don't mind advertising, as long as it's non-invasive. Invasive includes TV and radio, as long as the commercials are louder than the regular broadcast.