Won't find any arguments from me. Assuming he's healthy, this is a solid pick at a position that isn't necessarily a major need but could be upgraded. San Diego quickly has one of the better safety tandems in the league with this pick.
SB Nation's Bolts From The Blue explains the pick:
The plan with this pick after all the free agency moves was to go best player available. Mark Barron is that guy. The scouts over at Bolts From The Blue have been watching Barron closely since the beginning of the 2010 season. He's shown himself to a be a good playmaker, great at diagnosing plays and very good in run support. The Chargers have a prospect in Darrell Stuckey ready to take over the SS position, but Barron is a better talent. The Chargers need a player like that playing next to Pro Bowler Eric Weddle and helping out their corners who got exposed at times last year. One of the team's top priorities for the offseason was fixing their defense so that they are no longer last in the league on 3rd downs. This is a step in that direction.
Mark Barron 2012 NFL Draft Profile (via sbnnfl)