I leave my boat on a public/private beach - there is a bar near by that rents boats/waverunners. I have never had a real problem except someone stole a rachet block. I meant to take them off but didn't. I have the term "easily removeable high value item" that applies to my boat on the beach. I don't leave the spin pole attached (but WTF would someone else use that for?) I mainly worry about someone knifing the tramp ($$$$$) or stealing the rudders ($$$$$$$$) but so far I have been lucky. I don't leave my wheels there and I take off my port covers (I think the boat dries out easier that way).
It is all a calculated risk- I want to leave the boat on the beach so I don't have to raise and lower the mast all the time, nor do I want to take the rudders, downhaul, rotation lines, spin halyard, off all the time. more time is spent on the water and not rigging.
but then again, I guess I need to confess that I have raided a couple monohulls that have blown up on to the beach that no one paid the slightest attention to for months. Several shackles and blocks were obtained <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />