Just what we needed: another way to subvert our privacy preferences and browser settings. Evercookie is generating a lot of (negative) buzz on Twitter among those concerned with privacy. It was released a few days ago by Samy Kamkar, who describes it this way:

evercookie is a javascript API available that produces extremely persistent cookies in a browser. Its goal is to identify a client even after they’ve removed standard cookies, Flash cookies (Local Shared Objects or LSOs), and others. evercookie accomplishes this by storing the cookie data in several types of storage mechanisms that are available on the local browser. Additionally, if evercookie has found the user has removed any of the types of cookies in question, it recreates them using each mechanism available.

More info on evercookie can be found here.