Speaker baffles - good or bad idea?
 

I was wondering what is the opinion of the local car stereo experts about using speaker baffles behind door speakers.
When I installed my Focal speakers, I didn't use any baffles although the stock crappy 6x8 cones had some sort of a plastic half-shroud that's probably supposed to protect them from water dripping from above.
I saw some plastic baffles at PepBoys that are covering the back of the speaker completely. Is it a good idea to add such things to my Focals? How much would these alter the sound?
The last thing I want is to get water damage to my new speakers - or should I not be worried?

What do professional installers do for such cases?

Thanks.