Historically they have played Kobe at the 3. He will defend either position so it isn't a stretch to state that they will continue to do so. I think that it is a stretch that Farmar would get considerable minutes to create a situation where Kobe would play the 3 only because Lamar would have a hard time guarding some of the true 4's in the league.
The Lakers do have flexibility to play different positions when they work in their favor....a good chance to run a line up of Kobe/Lamar/Kwame in the front line would be against the Suns or Mavs when they go small during stretches of games. (I like Lamar against Marion or even Dirk for stretches)
But say for instance they play the Pistons or Spurs.....Lamar on Duncan or Rasheed looks like a definite mismatch in my opinion.
Lamar is a 3....so i think it is beneficial for the team if they allow him to play that position, because it gives him the best opportunities to be athletic and exploit the mismatches he creates. It would be nice if the Lakers could pick up a solid 4.....but that has been our weakness since the days of Horry.