I like the idea, Sean. It has tremendous scope for audience manipulation/annoyance. Let's say I write a song and call it Lord Bateman, and that it goes:
Oh, Lord Bateman, he was a green frog
He was a green frog of low degree.
A heron came and ate the bugger
So he never made it to proud Turkey.
Having sung it once you will be in a position such that when you next announce you are going to sing Lord Bateman all those spectators who run for the toilet whenever you announce a ballad won't know whether to go or not. If they stay, then you sing the Forty Verses and really piss them off.
I also see some mileage in going to your local Orange Lodge folk night and announcing you are going to sing The Foggy Dew. Then, if you find you are still alive, begin 'When I was a bachelor'. Or not.