Our own devil_fingers spent an inordinate amount of time creating his own methodology to evaluate catcher's defense based on throwing out runners, preventing wild pitches and passed balls, throwing errors, and catching errors. Not surprisingly, the three Royals backstops fared poorly: Pena was -2.9 runs in limited playing time, Buck was -4.8 runs in more playing time, and Olivo was 113th out of 114 at -8.8 runs (thanks Mike Napoli).
Nice article for the Wall Street Journal by Dave Cameron. Here's a nice quote:
"Over the last five years, the percentage of runners thrown out on the bases only has a .15 correlation with run prevention, which suggests there's almost no impact on a team's chances of winning (a correlation of 1 represents a direct relationship, whereas 0.0 shows there's no relationship at all).... So don't worry if your team's catcher throws to second like a nine-year-old. The best way to stop the opposing team from scoring is to avoid putting runners on base in the first place."