The most common cause of breast implant failure is fatigue and breakage of the implant envelope/shell.
This happens most commonly near a fold. Repeated folding-unfolding-folding at any one spot cause a weakness and then a leak. (This has been seen with airplane wings and other man-made structures repeatedly subjected to compression-decompression). Less commonly leaking is realated to a faulty valve in some saline implants. This was more common 20 years ago than it is now.
Breast implants are very resistant to compression. Being hugged, unless by a very powerful force (like hitting the steering wheel) will not cause rupture.
Because smooth implants are less stationary in the breast pocket than textured implants, their folds are also less fixed. As a result, textured surface breast implants are associated both with more rippling and with a higher rate of earlier leaking.
Unlike many other devices, BOTH Allergan and MENTOR, the producers of the majority of breast implants in this country, will replace all their implants FREE. Make sure your Plastic surgeon uses one of their breast implants and not a cheaper overseas implant. It will become much more expensive when your breast implants deflate.