I have know that from the day I installed Ghostery.
Since they were good enough to provided the service of blocking tracking cookies, I let them track me for a month, and then turned off the tracking feature.
Everyone that installed Ghostery should have known this.
The program works, and it’s easy to prove that it works.
I rather like the transparency of this add-on coming as a userscript ready install in Chrome: http://userscripts.org/scripts/show/35051
It makes the webbugs visible and one could analyse where they go.
When you find up such a webbug you can use ABP to block that image…
But if you have ScriptSafe installed, it also lists all your hidden webbeacons or webbugs it is blocking,
also all iframes and scripts, just hoover each to see paths)