It really depends on what you are advertising on PTC sites. At first I thought that it would be a waste of time until a friend of mine told me about how it benefited him. If you're promoting something similar to free money programs, like other PTC sites or GPT sites, they are more likely to join if the program gets their attention and if they're not already a member of the program. I promoted "paid forum" sites on PTC sites and I got a lot of referrals just from one campaign. When I promoted an affiliate site trying to sell something, I didn't get any sales. They are more likely to join a free program over anything else.