It would be great if there was a Firefox / Tor Browser add-on that could generate a hash of a web site's JavaScript and store it, and if it changes, it would pop up a big notification, warning the user that the JavaScript has changed. Of course, then you would have to trust the add-on maker. There are only four people that I trust in onionland, and they have all been around for over a year: DPR, the Bitcoin Fog admin, the Freedom Hosting admin, and maybe the Tormail admins. Any of them could go rogue or their servers could be taken over by LE in the future, but for now them seem legit. I don't trust random newbs who provide services, but I'm sure you'll find plenty of users among the Privnote crowd. A lot of people in this community don't care about their security and are willing to increase their attack surface with untrusted third parties (like you) for a little convenience.