You should have chased him!
The other day a C172 was doing strange manuvers around the city problably doing an airshow for his girlfriend, which I really don't mind, except he had not let anyone his position on the CTAF, he was going up and down like crazy obviously not looking anywhere but below, buzzing a house and then climbing to do a chandelles, stuff like that,
I decided to chase him to give him a hard time, when he first saw me he did the straight and level thing for a minute, then tried to dive, turn tightly, slow down, run, etc. etc. for about 10 minutes to get rid of me, when he saw I was not going anywhere but right behind him, he finally decided to head straight an level, we pulled next to him and he wouldn't even turn around to see us.
It was the most fun I had in a long time.
(Bell 407)