Of course, you just have to prove that you know the private key. Handing it out is unnecessary. My bad. BTW, instead of signing a message, you could also move

Of course, you just have to prove that you know the private key. Handing it out is unnecessary. My bad. BTW, instead of signing a message, you could also move around some money through that account. This may be easier to achieve for non-tech people, as it can be done with any Bitcoin client.