If I were famous I'd know what to expect and paparazzi would be counted as expected.
It seems to me that if the famous are friendly or on good terms with the paparazzi they generally don't get hounded. But if you are gun shy or do something really notoriously bad, they hound you like a dog.
Best example of this is of course the case of Princess Diana and the paprazzi's chase of her the night she died in that tunnel in France. If they hadn't been there that night would she have died in that accident? Probably not even though the driver was intoxicated at the time of the accident, but surely he wouldn't have been driving so fast as he did to evade the paparazzi that "chased" them into the tunnel.
Getting permission would be nice, but...if you're famous expect the paparazzi to be keeping a watch on you at all times.