Though adsense publishers, basically who are new to adsense often thinks of themselves as not only smart but over smart to cheat adsense and make money. But they often forget that adsense is more than what they can think of.
It is a common practice to adopt the ill means to earn from adsense. I was just browsing through the communities and find many communities related to click exchange. I was amaged to see the high member count in tgose communities. The basic practice adopted between the group members that they click on ads of each other to earn money from adsense.
May be they get success to make few cents from that but its not possible to achieve success with that because Google adsense is in constant effort of developing their algorithm to make adsense a safe place for advertisers and the publishers as well thus giving a soothing experience for both.
How adsense traces fraud clicks.
Though adsense never declares about their strategies but a close observation reveales the probable explaination for the question.
Adsense counts the clicks as Invalid clicks when
* Clicks are being made from same IP which is being used by publishers within short duration of posting a blog/webpage.
Exception -But Adsense is quite wise enough to distinguish between genuine and fraud clicks. It has developed algorithm to trace genuine clicks as a publisher may use cyber cafe for using net and the clicks generated from the same IP is generated.
* Clicks generated daily on a particular website from a particular IP as in the case of click exchange by friends and relatives of publishers from different IP other than that of publisher.
* Multiple clicks on adsense ads of same or other pages of same website within few seconds. As it is a common sense that if the click is genuine, then the user would take quite satisfactory time to read the website opened by first click and comeback for second click or third click.
* Image Adsense codes placed next to image of blog or website is considered as invalid click as this is against the TOS of adsense service and forces the visitor to click on ads by frauding.
* Click on a high paying keyword ad on the webpage/blogpost just uploaded may be considered as fraud click, as it takes time by any pages to get listed on search engines and the click on such ads no sooner it get uploaded may be considered as fraud click.
* High click ratio with very little visitor counts from few IPs within few hours or even in a single may be considered as fraud click.
Once again it should be rememberd that these conclusions has been reached based on the huge community responses of cheaters found on many social networks where someone claims to have clicked on the ads of other group member but the 2nd user on the other hand has not earned even a single penny. Adsense has never disclosed any of the strategies of counting fraud cliucks.
So, its better to spent time to create better quality content to give the reader a soothing experience instead of spnding time to create click exchange communities as these communities are not successfull at the end of the day and may have very severe consequense of getting permanent banned from Adsense.