Personally I think account sales are dubious simply because you can't put them in a secure trade window. Houses, rares etc can be. In addition, expensive items can be purchased off vendors.
Items over 120 mil, of course, pose a problem and require trust through the form of a broker. I really think that there should be cheques for higher amounts in UO to avoid potential issues that this can cause. However the issues relating to account sales are much harder to circumvent and anyone who buys an account for gold is wide open to abuse.
All that the original owner has to do is to do is contact EA Customer Support, give their account name and the last method of payment and they can claim their account was hacked. This, I think, even applies if the account creation code is in the hands of the new owner (although this is something I would always hang on to with an account of value).
I'm not against account sales for gold but it is very risky. That account name will always be known to at least one other person; the previous owner. Maybe other people know that person too or maybe someone sold them the account before. Some account names are easier to guess than others and there is a possibility that the previous owner could have their computer compromised and the UO account folder snooped through. Given that scenario, then, it could even be possible for someone to have access to all the previous owner's financial details and use them to reclaim an account.