I posed the question in reply #71 to Dave Cameron today in his chat. Below is the exchange:
http://www.fangraphs.com/blogs/fangraphs-chat-42413/
Cameron is on to something. A quick look at DE's O-Swing% from 2011 - 2013 shows it has gone from 32% to 40.5% to 46.1%, while the O-contact has gone from 61.6% to 55% to 60%. In other words, his best offensive year, 2011, he was swinging at a lot fewer out of strike zone pitches, while now he is not only swinging at more than last year, but he is also making more contact. That helps explain more dribblers and pops.
It's not just swinging at pitches out of the zone, he's also making contact at nearly the same rate as 2011. Simply put, 30% of all of his at bats end with him hitting a ball he shouldn't have swung at in the first place.