It would help, but you'd lose a ton of speed. Depending on who you connect through, you could be looking at just slower-than-normal all the way down to slower-than-dial-up. Definitely not good if you want to do large downloads or torrents (the latter of which is generally considered to be a no-no on the Tor network).
I honestly wouldn't recommend it. It's a nice concept, but the connection speeds of the contributors are too varied for it to really work well.
