...for being bad at throwing out baserunners. Barajas threw out 6 baserunners this year while allowing 93 stolen bases. Since 1960 (as far back as the stats seem to go), no other catcher who has caught 700 innings has thrown out as few baserunners (though Barajas himself pulled it off in 2010, with only 34 SB).
The only catcher who ever approached Barajas's awful CS% was Josh Bard in 2007, with 10 CS to 121 SB.
Thanks to jrhouse8 for asking the question.