How will you differenciate between a PPC and PTC

@Mash99 (365)
Pakistan
October 15, 2008 12:11am CST
How will you differenciate between a PPC and PTC business in terms of a corelation between the two but the legitimacy issue is quite opposite. PPC like google, yahoo, adbright and others you know thier reputation on the other hand what will you say about PTC...???
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