To summarize: You can sell nyms by transferring private keys. Whether other people like it or not, it can be done. And others can't necessarily tell. There is nothing to stop someone from transferring his private key in this way. Any reputation goes along with the nym, and this may be quite valuable. As Wolf points out, building up a reputation is a lot harder than maintaining one. The main problem is how to do the transfer cleanly, such that the former nym owner can't damage the reputation once sold. Several solutions have been offered, involving doing a key change. Complications arise in terms of making the old key useless, but these can probably be worked out using careful timing, as well as escrow services. Here is another way to handle it: meta-reputation. This is your reputation for reliably handling reputations. Someone who has done several nym transfers cleanly and honestly could build up a meta-reputation and this will facilitate future nym sales. Meta-reputation cannot be solely associated with a particular nym, but via transferrable credentials it can build up over a family of nyms which are unlinkable. A nym seller can present credentials showing that it has completed successful nym transfers in the past, honestly and without problems. This offers evidence that a proposed nym transfer will go smoothly as well. The problem of selling meta-reputation is left as an exercise for the reader.