I dont think anyone ever has. Everyone selling their traffic and asking for the money up front usually has absolutely horrid conversions they dont want you to know about, and can make more money selling it than sending it to ARS like everybody else.
I'm really sick of getting email spammed from webmasters saying "I will sell you a spot on my TGP for $3,000 a month, its a bargain!"
And the thing is, they do it because theres people out there who take the gamble. Convincing them to put up your link on a pay-per-signup deal is hopeless, and the dodgy car-salesman like webmaster always has excuses. Usually something like "I dont know if i'll get paid!" ..
And when you tell them that anyone asking prepaid amounts of traffic is a scammer, my all time favourite comeback was "Sex.com do it!"
So, lets hear everyone elses experiences with prepaid traffic deals!
this ought to be a laugh..