My personal gripe is any TV magician who relies on camera cuts to enhance the effect. for the viewing public - Doctor Who has camera special effects, and thats where they should stay. Hey, I can fake photos with photoshop. Magic should be 'real' ... if you get my drift.
So I am afraid that David Blaine's levitations are my gripe of choice.
My close runner up though is any children's party entertainer who does kids magic but doesn't recognise there still needs to be art in his or her work. You know the ones ... those people who buy a few mechanical tricks down the joke shop then charge the earth at kids parties just to make a few quid back. I have worked with children for years, and not just with magic, and they deserve as much a high quality work and presentation, if not more (its harder to misdirect kids sometimes!) than with adults.
Nuff said
(I will now head for the bomb shelter as a plethora of kids magicians come after me with sharp implements

)