Depends, because the term "preamp" refers to a variety of functions. Many preamps for bass use have little or no overall gain, and are intended to provide signal conditioning while remaining compatible with the signal input of a bass amp. On the other hand a preamp designed to feed the input of a power amp may have a relatively high output level that could overdrive the signal input of a bass amp unless one is careful with the gain controls. In this case distortion is more likely than outright damage.
Preamp + Preamp = ??? 
Using a pickup with an outboard preamp plugged into a amplifier that already has a preamp stage built in... what do you get???
