I wrote interference but technically meant obstruction - just edited. The main example I would give is when a catcher uses part of his body (often his leg, but sometimes his entire body) to block the plate when in reality he didn't need to occupy that position to receive the ball (which the rule allows him to occupy the space needed to receive the throw). For example, a throw is coming in from the OF (particarly CF or RF) and is headed for the 1B side of the plate. In the meantime, the catcher positions himself on the 3B side of the plate in order to block the runner but has to reach back across the plate to catch ball. The throw isn't so far offline that he has to move himself off the 3B line in order to catch it, but in reality, he didn't need to occupy the 3B side (and outright block the plate) in order to receive it. You never see this called obstruction, but I would argue in many cases he didn't need to occupy that space in order to receive the throw. The only reason he occupied the space was to block the runner - it was actually otherwise a less than preferable spot to be if one was simply receiving the throw.
Basically, my view is just because you can put yourself in the runners way while still being able to reach out to receive the throw doesn't mean you should have full liberty to do so, not if it wasn't necessary to receive the throw. The language of the obstruction rule doesn't necessarily need to change, but if we're going to basically make all runners slide, then I'd like to see the existing obstruction rule interpreted/applied more strictly.
[This message has been edited by DannyDuberstein (edited 11/13/2013 1:20p).]