It is irrelevant if bob123 is a rival account seller or not. He still used deception to destroy the property of another. The point of the analogy is you can cause financial damage to others without direct financial (or any financial) incentive. It is in fact equivalent to burning his product because it is now valueless as a result. The fact that account sellers need to keep their products from being revealed is 100% the result of the fact there are dozens of people on this forum who feel it is their right to go around policing the forum by whatever arbitrary metrics they deem valid rather than the forum rules. It is circular logic. We need to destroy his product because we run around destroying his products.
No, they need to keep the exact product a secret or it loses it's value to sport a reputation and credentials that were not properly earned by the buyer. Whether that be a rank, post history, merit history, or trust ratings. Most people buy them so that they can get into a signature campaign that they would otherwise not qualify for. There is the potential someone could use the bought account to do a whole lot worse. Can you imagine the damage that could be done if either you or I sold our account in secret?
Edit: Since it appears everyone wants to use analogies, let me use this one. Suppose it came to my attention that a particular individual was selling birth certificates and social security cards. This individual acquired them from the rightful owner's, willingly, by purchasing it from them. I decide to take it upon myself to pose as an illegal alien and pretend that I am interested in buying one of these documents. I request that the individual let me see one of the documents and I memorize some of the details. I then make some kind of excuse to back out of the deal and then promptly report what I know to everyone that I can think of as well as the authorities. By this act, I have not only destroyed the value of the product in question, but I have likely destroyed the person's entire enterprise as well. Would that make me a "scammer?" I think not.