In addition to what other have already noted, one other thing to keep in mind: The Tor exit node that happens to handle any particular request gets to read the

In addition to what other have already noted, one other thing to keep in mind: The Tor exit node that happens to handle any particular request gets to read the relevant traffic (since it is handling the request to the actual end server on your behalf). So, for instance, if you're logging into some bulletin board via unencrypted http, the Tor exit node handling the login request gets to see your username and password on that bulletin board in cleartext (as can all the other net infrastructure between that exit node and the bboard itself). In one sense, this doesn't change your risk profile; if you're logging in over unencrypted http directly, you're also at risk of sniffing. However, the risk may be enhanced with Tor; there are persistent rumors of law enforcement and intelligence agencies (and others with darker-colored hats) running exit nodes which deliberately sniff the traffic they're proxying to see if something interesting comes up. It also might be possible for such a hostile exit node to mess with the content of unencrypted traffic, though I've personally heard no rumors of that. Note that if you're using Tor to proxy encrypted traffic (https), the exit node sees only the encrypted data stream, which is as secure as the encryption you're using --- and the official Tor browser bundle includes the "HTTPS everywhere" Firefox plugin to try to get you to use HTTPS where available. Additionally, if you're using Tor, anyone monitoring the net segments between you and the entry nodes you hit may be able to tell that you're using it (though they won't be able to tell what you're using it for). If the local secret (or other) police frown on that sort of thing in principle, it could be trouble.