I think the take-away here is that if you're going to use a trick like this, it might be in your best interest to be transparent with your users and offer a way for them to remove all of this information. Of course, if you're using this particular hack then you probably don't want your users to remove the cookie to begin with.
Comments
I think it's appropriate to mention that the New York Times just ran an article covering some lawsuits related to tracking users:
http://www.nytimes.com/2010/09/21/technology/21cookie.html?p...
I think the take-away here is that if you're going to use a trick like this, it might be in your best interest to be transparent with your users and offer a way for them to remove all of this information. Of course, if you're using this particular hack then you probably don't want your users to remove the cookie to begin with.