enigma1 - 12:49 pm on Apr 6, 2012 (gmt 0)
It's Google via your site's analytics js or other script you integrate with your pages. To normal visitors it looks like your site does this, don't expect them to check the cookie domain origin on their browser.
And for this reason browsers have some global cookie controls to set whether or not third party cookies are allowed or not. As far I know the default is off for years now.