It's unclear what Jackson did to draw the league's attention; Jackson and teammate Derrick Brown were assessed technicals during the game, and the Bobcats shot just 11 free throws all night. The Pistons had 27. Jackson had five personal fouls on the night, as well.
It's worth noting that $50,000 is a substantial fine when it comes to dealings with referees. Coaches and players who criticize officials in public remarks are typically fined up to $25,000. Heavy in-game criticism results in a tech, which comes with a $2,000 fine. Jackson either pushed the boundary quite hard, or the NBA is drawing a line. Without details on what Jackson did, we won't know which is the case.
Update: Speaking to the Charlotte Observer, Jackson sounded off about the hefty fine: "I walked off the court, upset about the outcome of the game. I guess they had a camera following me all the way to the tunnel, where I wasn't even in sight of the referees, and read my lips. I guess I can't talk to myself. I got fined for talking to myself."
Speaking of player protestations, we're a couple weeks into the NBA's new war on complaints, as the league announced it had directed its referees to hand out more techs as players and coaches demonstratively disagree with whistles on the court. There's no way but our eyes to measure whether complaining has subsided, but it's worth noting that refs have assessed 69 techs in 78 games, or 0.88 per game. Last season, refs handed out 0.6 techs per game.