This topic was inspired by the Someone else is singing "my" song[i] topic and guy totally 'effed up David Bowie's[i]Modern Love last week at my regular Thursday hangout.
While I agree that no singer "owns" a particular song in a songbook, regardless to how well or often one my sing it at a particular establishment, I'm that we all have songs that we love and just hate to see FUBARed by singers who are, dare I say, less accomplished.
Songs that if you could, you'd want to protect in someway!
To that end I've come up with the idea of "The Preemptive Song Request Slip" for karaoke "regulars". You'd give your KJ a list of 4-5 of "your" songs. If some "poacher" put your song in, the KJ or replace whatever song you had in rotation with your preemptive and would then inform them that it's already in and that they need to pick a different song. You would of course then be obligated to sing your "preemptive" song.
Anybody feeling me on this?
Songs I'd list as Preemptives if I could.
Don't Let The Sun Go Down On Me Elton John
Ballroom Blitz The Sweet
Modern Love David Bowie
Black Pearl Jam
Rosalita Springsteen
on occasion I will protect a "regulars" song that I know he/she ALWAYS sings. ... I believe I run a fair show 
but I understand the singers who want to sing THIER song. 
Most of the regulars have a stack of songs they sing so it is not usually a problem if
But then again, if the guy wanting to sing my song can sing better than me, and the KJ knows it, then by all means PLEASE Mr. KJ, step in and take appropreate action. 
I know what you're thinking, and you're right. But like Emorej said, "A guy CAN dream, can't he?"