It's a no-brainer that Facebook, Bing, Google etc. have high quality traffic. However, what about stuff where they promise a lot of visitors for a laughable amount of money? Do you believe it? Well, I don't want to be totally cynical as of yet, but I think the source of the traffic matters.
I don’t believe it until I see proof of where the traffic comes from. I know that tunblr, reddit and quora can be good sources of extra traffic as well.
These companies often use pop-unders to get traffic. Another source is redirected domains. Anyway, it's not as targeted as traditional sources because people seem to "stumble" on your site.
