I really can't understand why Brown would decide to opt out. It's not like he'll get way more from other teams... And being in LA offers more lucrative opportunities than other markets offer.
Maybe he doesn't want to play for Mike Brown? He struggled when Brown coached him in Cleveland. Him and his agent probably want to explore other opportunities for more money and more PT. Maybe those rumors with him sleeping with Gasol's fiance have made it awkward for him. I'm surprised any player with a reasonable contract would opt out with the CBA up in the air.