I've never been to a Dodger game or Lakers game in LA, but I have been to a number of mixed martial arts events in the city... and I'm sure the situation is a little different because of the difference in sports, BUT... every single time I've been out there for events there have been slews of people selling bootleg event/fighter shirts outside the various stadiums and arenas with just a big stack of shirts slung over their shoulder.
Nobody seems to care.