BetterPrivacy is a Firefox addon that prevents storage of non-deletable ‘super cookies’. These super cookies are used by Google, YouTube, Ebay etc. If you are concerned about your privacy and the trails you leave on the web while browsing.
I was not aware of super cookies until I came across BetterPrivacy, but a quick Google search does turn up a Wikipedia page on local shared objects (emphasis added by me):
Flash Players use a sandbox security model. Adobe Flash Player does not seek the user’s permission to store LSO files on the hard disk. LSO’s contain cookie-like data stored by individual web sites or domains. Any kind of text data can be stored, some of which may be cause for privacy concerns. Indeed, as with cookies, online banks, merchants or advertisers may use LSOs for tracking purposes.
More than security concerns, it is the tracking element that would worry any internet user. Flash cookies are placed in system folders, thus protected from deletion.ADVERTISEMENT
BetterPrivacy removes LSOs on every browser exit. Much like Flashblock and Adblock, BetterPrivacy is an install-forget addon – you do not have to do more than configure it initially.