Let me just vent for a bit here.
One of the most enjoyable trends in cricket is for commentators to only refer to yorkers when they don't get hit.
Start with our favourite, Sir Geoffrey...
England were bloody stupid against Australia - their World Cup campaign is already in crisis - TelegraphIn the last seven overs we bowled only seven yorkers. Three were not scored off and four went for a single. Perhaps that tells you something.
Well, I for one remember Jimmy Anderson being taken over cover off a ball that was about fifteen centimetres short of Maxwell's foot. That's a yorker, it just still went for four.
Secondly, people keep talking about the ramp as though that's why bowlers fear bowling the yorker. The real reason is the change of natural technique. Think of most of the guys who you watched growing up - from Greg Chappell, Gooch, Gower, even through to Mark Waugh - you bowled the ball at off stump and it went through mid-wicket, or square leg. This generally saw the front foot line up with at least middle stump.
Picture a ball that is super full, that will only get up to halfway to your knee. With your leg in line with the ball, you have to hit across your pad, your impact zone is suddenly ten to fifteen centimetres in front of your pad, and you can't generate any power. That's even if the guy misses the yorker, whether it be short of it or a low full toss.
Guys nowadays set their techniques up to hit the ball back where it came from a lot more. Watch Mitch Marsh - he sets his left hip up back to the bowler all the time, and it feels even natural to him to push it towards mid-on. This allows guys to hit the ball after it's gone past his pad, even if it is a yorker - underneath his eyes like a golf shot, the most powerful spot of all. This has been the most important reason why the yorker is being "hunted" - the time of "a low full toss is still OK" or "still full enough to not be able to get under it" doesn't exist anymore.
Thirdly, by bowling short you are hitting a target ten metres away, with a better idea of controlling the scoring zones in a lot of those cases, especially when you only have four fielders to spare. If you miss that target by 10% (lets say), the actual distance that you miss the initial target by is less, hence the batsman is still likely to play the shot that you are hoping for, and you bring the natural variation of the wicket into play.
When you go for the yorker, and miss by the same degree (10%), the variance is much higher over the longer distance, and more likely to be punished.
Fourthly, this effect is multiplied for taller bowlers. A taller bowler missing the yorker by a small amount ends up providing much more vertical angle to work with. Following on from England's success, teams have gone searching for height in their quicks. Thus, there are a lot more quicks who are vulnerable to being taken to with the yorkers.
That's it, the case for the defence.