i think it would be better that fans be able to keep the ball. i actually caught one at each of two different matches i was at in IW. i was sitting in the front row where the ball would always go when the player would hit a big overhead i guess.
they never made me give the ball back i dunno why. when my dad caught one during one of those matches he threw it back (he was sitting right by me), but they never like motioned at me to give it back so i kept it. maybe it was like at the end when they were gonna change balls anyways ot something, but i dont really remember