If I take a job as a hit man, and I always manage to kill my targets I am also making my customers happy, but I would hardly claim that I was being ethical.

{edit} To expand on that, the legality of what is being done doesn't matter either. There are many unethical things that are still legal (e.g. patent trolls, large companies burying competition through using the legal system as a money drain, suing someone for defamation/slander just to shut them up about something that is true but you don't want anyone to know about, etc).

And it wasn't 'above the board' either, because it's not like they told the restaurant what they were doing. If I call ahead and book a table for two that I have no intention of using unless I can scalp/pawn it off on someone else, how am I being ethical by lying to the restaurant? {/edit}