Here's a theory, based on personal experience and observations: with increased studying by hitters of pitchers (through video and scouting), a pitcher needs to disguise his pitches to be successful. This has led to less throwing of pitches such as curveballs where the elbow is cushioned (and less disguise) and more throwing cutters where the elbow is not cushioned (and more disguise). I've noticed (in general) MLB'ers returning from TJ surgery are more susceptible to tipping pitches, whereas others have the same violent snap look on fastballs and breaking pitches. Mike Pelfrey is an example of a post-TJ pitcher, where I can tell if he's throwing a fastball or offspeed based on his motion. Perhaps this is how most pitchers threw before micro-analysis of every aspect of the game.