A lot of people have been using services like StatCounter to track AdSense clicks as well as for gathering other information about their website visitors.
StatCounter is the most popular free service that offers the ability to track AdSense, Amazon and other affiliate ad clicks but I don't mean to single them out. I think it's a bad idea in general to give access to information about your site's visitors and what AdSense, Amazon or other affiliate ads your visitors click on. It is something that could potentially reduce your earnings.
Not many things in life are free and it's hard to imagine a company is giving you access to their service and not getting anything out of it. They have servers and bandwidth to pay for as well as salaries for their staff.
StatCounter claims that they make their revenue through advertisements on their website, they do not put ads on your site and you can even have their tracker hidden so it's not visible on your website. But is StatCounter getting more out of the deal?
The answer is obviously yes. StatCounter is getting something a lot more valuable out of the arrangement.
According to their Terms and Conditions for using their service StatCounter retains ownership of all visitor data they collect from the websites that use their service. That means all the information about what pages on your site are visited, how visitors find those pages, what visitors our clicking on those pages, what ads are being clicked, etc.
Webmasters and AdSense publishers are generally secretive of about what pages and niches perform best for them in terms of advertising revenue so I'm surprised that so many would choose to give that information away. When you use a service like StatCounter you're letting someone else know the most effective ways you use to get your traffic and what content has the best interaction with visitors in terms of ads.
StatCounter doesn't indicate what they do with that data but since they own it they can do whatever they want and it's not difficult to imagine different ways to use that data for financial gain.
It's an important point so let me repeat it. StatCounter is in possession of data that can tell them what types of pages generate the best search engine results as well as what pages generate high advertising click-through-rates (CTR).
How StatCounter Can Be Used Against You
Let's say you have a blog about your favorite hobby, something obscure like trimming your toenails. You have the site monetized with AdSense and Amazon's affiliate program and you choose to use a service like StatCounter to track your visitors and help you optimize your ad placements.
Your site becomes wildly popular and has higher than normal revenues from both AdSense and Amazon. What harm would it do if someone had access to that information?
Let's say I had access to that information. Since I see you're having a lot of success with that obscure topic, and I myself am familiar with toenail trimming, I could easily create my own blog on that topic and monetize it in the same way which could reduce your earnings by you losing some visitors to my site. The amount you receive per click can also go down because there are now more spaces where advertisers can advertise.
That was just example to indicate why the information is valuable. There are easier ways to monetize that data than by creating copycat sites. The one that will hurt you most is if sites like StatCounter are or start selling that data to others. Doing so is not prohibited by their terms of service.
Imagine a service where users pay fees to have access to data that shows what niches don't have a lot of competition, what niches have high ad click-through rates. That service would be very valuable.
The big content publishers, that have more traffic, search presence and clout than your little blog can see how well your niche is doing and start publishing content for it, cutting into your bottom line.
Not only is it bad for you, it's bad for the Internet in general as it's filled with more redundant content that dilute the information coming from what might be more authoritative sources.
keep information about my sites' SEO and advertising performance to myself
I prefer to keep information about my sites' SEO and advertising performance to myself as much as possible. For my websites, I track visitor's usage and interaction through utilities that analyze my server logs such as AWStats and Google Analytics.
Google Analytics is a third-party tracking application but I don't consider it to be as harmful because Google already knows a lot about my websites traffic and ads because many of my sites use Google AdSense.
I haven't looked to see if StatCounter or any other service is actually doing what I said could be done but it's they're not prohibited from doing so and it would be the most financially rewarding use of their data. Hard to think there isn't a plan to take advantage of it.