Hi BDLJ,
In truth, watches can leak from anywhere, and I've seen them leak through the crown, the tube, the pushers, the pusher tubes, the back gasket, the crystal gasket, the bezel gasket, the crystal itself (cracked or chipped) or even the case frame itself (corroded pores or half-assed diamond studding).
The crown is the most common culprit though because this it the one the user interacts with the most. Whether through leaving the crown unscrewed or pulled into setting position and getting when submerging the watch or simply wearing it out or damaging it in some way from use and abuse, the crown and tube are the most common failure points in my experience, but this really depends on the case design to some extent.
Some ultrathins will commonly flood around the crystal or the back due to the flexing of the case and many non-round cases will flood around the crystal or back crystal gaskets because it's VERY difficult to get a hermetic seal around a non-round crystal (glue helps).
_john