There are hundreds of thousands of advertising companies out there, and 90% of them are dishonest and take advantage of advertisers! They do this in many ways, I will outline some that I am familiar with and have been a victim of even with some of the bigger players who have ripped me off as well as others!
I have used a lot of advertising agencies to find some I liked, in the process I encountered one which shall remain nameless we ran them for 3 months completely legitimately on our game website and they waited until we reached the payout and banned our account with no explanation no response to E-mails. When I finally contacted them by phone a couple months later I asked why and they replied click fraud which annoyed me as we had not! Then I asked what had become of our 50$ had it been returned to the advertisers? (if they believed the clicks we fraudulent would it not make sense to return the wasted money to advertisers?) When they replied “no” I promptly hung up the phone on them and embargoed them! They stole 50$ from me as well as the 50$ from advertisers without even telling them!
Now you may be familiar with “Paid-to-Click” most Internet users are! I have logged using 3 or 4 systems the amount of hits received and only on one site out of about 10 did I get the amount I paid for. When I approached each site they told me in case of discrepancy between my “inferior” counter and theirs, theirs would be considered correct, ya 25$ worth of correct! I had 4 reliable counters as well as 1 or 2 extras! No way they were all wrong!
The final fraud of online clicking advertising be it Paid-to-Click or just a text advertisement on a page is the fact that 70% of ALL clicks are fraudulent, this includes asking friends and members of websites to click or just plain clicking for fun with no intention of continuing on to buy or act. I cannot directly quote a source on the 70% but I have seen it consistently in my travels and it seems a very fair judgement. It amazes me how many companies still participate in cost per click advertising with the low turn over rate, the highest conversion rate I have ever received was a two-bit game advertising company at 2% conversion to joining my game and this was from prime gamer real-estate!