I once sat in an icecream parlor watching a group of monkeys destroy everything they could grab hold of on a somewhat new car across the way. Thing lost its mirrors, antenna, hood ornaments, logos, and ended up with more than a few scratches and dings.
I also once saw a monkey jump at a lady, yank off her purse, and the search the contents while another monkey kept harassing her.
Monkey's are evil scheming creatures. This might be why many "trained" monkeys are done so with alcohol. This is actually something of a problem in Thailand where there are actual monkey rehab centers.