Are you talking about just engraving, or inlay? Both can be done on the back of the neck, but the curvature does make it more tricky. I haven't had a request to do one yet, but I have seen Aaron's work on the back of a neck. I think he did someone's name in kanji.
As for the name thing, very true. There's a growing number of ukers out there, but finding someone else with the same name, who wants your uke, with the name on it is hit or miss.