You can easily configure Bitcoin to connect though Tor (in Options -> Network, turn on "Connect through SOCKS proxy" - the default proxy settings are for a standard Tor installation, though you will need to change them if your Tor setup is non-standard). You can also
run Bitcoin as a hidden service, though (I'm pretty sure) other Tor nodes won't be able to connect to you automatically - to connect to hidden Bitcoin services, you need to
manually set up each hidden service you want to connect to.
The
wiki says that "...the network won't work if everyone does this. BitCoin requires that
some country is still free." though I have no idea
why it won't work. It seems to me like it should (though it would require some effort set it up), but maybe I'm missing something obvious.