Intresting document on Cryptome bout how Bitcoin over Tor Isn't a Good Idea:
http://cryptome.org/2014/10/bitcoin-tor-nope.pdfBitcoin is a decentralized P2P digital currency
in which coins are generated by a distributed set of miners
and transaction are broadcasted via a peer-to-peer network.
While Bitcoin provides some level of anonymity (or rather
pseudonymity) by encouraging the users to have any number
of random-looking Bitcoin addresses, recent research shows that
this level of anonymity is rather low. This encourages users to
connect to the Bitcoin network through anonymizers like Tor and
motivates development of default Tor functionality for popular
mobile SPV clients. In this paper we show that combining Tor and
Bitcoin creates an attack vector for the deterministic and stealthy
man-in-the-middle attacks. A low-resource attacker can gain full
control of information flows between all users who chose to use
Bitcoin over Tor. In particular the attacker can link together
user’s transactions regardless of pseudonyms used, control which
Bitcoin blocks and transactions are relayed to the user and can
delay or discard user’s transactions and blocks. In collusion with
a powerful miner double-spending attacks become possible and a
totally virtual Bitcoin reality can be created for such set of users.
