I tried using them way back in the day. They banned me for some reason. Something about invalid clicks I think. I never tried to cheat the system and tried to appeal several times, they never accepted the appeal.
They have changed the policy since then. I was banned once myself, but I was able to make a new account and it seems that a lot of the issues surrounding improper banning have been mitigated.
Honestly, one of the biggest issues I have had, as of late, is honestly clicking my own ads - sincerely by mistake - simply because the little buggers would sometimes catch me off-guard (I have had to some adjusting to keep the ads a certain way, not embedded in the text, not pop-ups, etc.). Also, in general,
my website is obviously a website I visit very frequently. With how intrusive and "all knowing" ads have become, it isn't uncommon for them to recommend me a sale for a WordPress theme I want or something I may want to look at. (I usually just go to the website directly in that regard, but I'm just saying.)
I have found that they haven't held it against me and simply recognize that I was the one to click it and thereby negate it (don't pay me for the click), which I appreciate.
Ads, in general, pay a lot less than they used to, however.
I had one forum that did relatively well and was able to pull in a couple hundred a month around a decade ago, and that was without a concentrated effort on viewership or advertising our website anywhere. Nowadays, I have trouble getting one-hundred a month on certain sites, in spite its much higher viewership count and I *do* put a lot into viewership and advertising.