NBA referees tend to favor the teams who are agressive without being obvious and if they don't complain. When the Lakers were aggressive in the beginning of game 4 they got the calls. Later when they became passive and started complaining they didn't catch a break. If Kobe actually started to get the ball inside early on the clock when the Celtics go small, the Lakers would get a ton of calls with Odom and Gasol going to the line. With kickouts to Kobe who would then drive, Kobe would live at the line.
However when the Celtics "get set" on defense, the Lakers are going to get few calls. And on offense, the guys like Powe, Pierce and Perkins are always going to be aggressive unless the Lakers play solid man up defense.
Remember this: Talent only gets the calls when they work as a team to create aggressive situations.