SpaceX decided to not use explosives to stage separation (because its' too unpredictable), but the side effect of using only hydraulics is... that they do not produce new space junk which will orbit of the Earth...
... but they are actually pioneers in sending "junk" to orbit of the sun and some day this will cause a situation like that (watch from ~2:30 ) :D
RE: Space Junk: It's Much Worse Than You Think | Answers With Joe