Does online anonymity really exist?

In the process of pimping my myspace profile (yes I’m into it please don’t slam me), I came across a number of sites solely dedicated to profile tracking, such as www.trackmymyspace.net and www.whosonmymyspace.com. Such sites claim to be able to give you information about who has visited your profile, ie. when they visited, the ISP they’re using, and their computer’s unique ID! I investigated this tracking thing and it seems we’re never completely anonymous when surfing, that our computer’s ID is transmitted with every click... A BBC article used the term "Big Brother" to describe how every online move we make is recorded (see http://www.bbc.co.uk/webwise/column/column050104.shtml). Kinda frightening I think...