Any 'performers' who use a music stand and crib sheets.

Attendees at sessions who fidget with their loose leaf anthologies whilst someone else performs thereby distracting other listeners.

Instrumental players usually whistle or flute who play mechanically from the music note for note but have no knowledge idea concept of phrasing emphasis thats not a desease - please insert you own punctuation marks

People who heckle and think themselves hilarious when a floor singer is trying to compose themselves for the performance of a lifetime of a song they just learned, and have been gearing themselves for a period of time.

Floor singers who havent planned what to sing

An audience !!!!! usually in a pub gig - that do not applaud or only clap twice cos theys ignorant

Passers by in the street who have no appreciation and think the busker is beneath them, when all the time....

Drunks with pit bulls who sit close to you when busking, and the dog gets to be patted by very small children with very young mums and you can see that the dog is thinking.
'Lunch?'

Under-rehearsed performers.

Anyone singing Streets of London a capella and other similar well known 'Done to death songs'

People who arrive on the scene and immediately interupt other people 's conversations,

My old english teacher from school

My old P E teacher - Ryan by name - too who was miffed that I went to the college he'ld gone to and cos I smashed him at badminton. And I got better results and my students, well some, achieved greatness. Up yours Ryan

Thats enough for now, more later.