This is not really "visitors" - more like "hits".
No one opening the webpage will give one care about your site, or will even read it for a fraction of a penny. They have multiple browsers with multiple tabs open and keep each page open just long enough to get their tiny reward, without even looking at it. That is, if they are real people who signed up on your site and not just paid traffic from somewhere else.
This is simply false. Our visitors are verified by captcha and we take many other security precautions to ensure valid hits from engaged users. The conversion rates of our visitors is absolutely astounding. We receive tons of feed back from happy advertisers and users all the time.