In terms of protecting your anonymity, even when correctly managing cookies you may be uniquely identifiable by browser fingerprinting: https://panopticlick.eff.org/
At least the last time I looked, the network appeared quite thin, with much of your traffic by default traveling through a small collection (perhaps as low as one) of exit nodes.
TOR also represents a juicy target for eavesdropping by its nature as a concentrator for people trying to avoid it. If you were a burglar, it would make sense to stay the hell away from a place the cops had identified as a hotbed of burglary since they'll probably be concentrating their efforts there.
Most of these things apply to other possible solutions, but at least there you may get the advantage of most users of those services "having nothing to hide" making them not as juicy a target.
If I was super, super concerned about my privacy and anonymity when sending a specific few documents or such, I'd most likely take a page out of the black hat handbook and compromise a few lightly administered servers and use a not commonly used covert channel.
The EFF themselves present many of the problems: http://www.torproject.org/download/download.html.en#warning
On top of that, the EFF has demonstrated that they are worried (reasonably) about the trust given to the global CA structure: http://www.eff.org/deeplinks/2010/03/researchers-reveal-like...
In terms of protecting your anonymity, even when correctly managing cookies you may be uniquely identifiable by browser fingerprinting: https://panopticlick.eff.org/
At least the last time I looked, the network appeared quite thin, with much of your traffic by default traveling through a small collection (perhaps as low as one) of exit nodes.
TOR also represents a juicy target for eavesdropping by its nature as a concentrator for people trying to avoid it. If you were a burglar, it would make sense to stay the hell away from a place the cops had identified as a hotbed of burglary since they'll probably be concentrating their efforts there.
And, of course, there is the issue that it's been used in the past to publicly out users traffic: http://www.theregister.co.uk/2007/09/10/misuse_of_tor_led_to...
Most of these things apply to other possible solutions, but at least there you may get the advantage of most users of those services "having nothing to hide" making them not as juicy a target.
If I was super, super concerned about my privacy and anonymity when sending a specific few documents or such, I'd most likely take a page out of the black hat handbook and compromise a few lightly administered servers and use a not commonly used covert channel.