#1
I just recently noticed this on my accoustic, there are little chips in the bridge (it's some kind of plastic type stuff) where the strings go over it. I'm thinking it's caused by tightening the strings when I put new ones on or if I change the tuning (which I don't do often). I tried to take pics but my camera wouldn't focus properly so I quickly ms-painted it :



The top one is a top-down view, the cream colored part is the bridge (or at least teh raised part of it that the strings actually sit on), the red portions are where the little chips are.

The bottom one is just a front view of the plastic part. Again the red is the chip, so with both you can get an idea how big they are.

Everything still works and sounds fine on it, I'd just like to know if this is something I should get checked out/fixed or just leave it for now unless it gets worse.
#2
as long as it isnt affecting sound or playing then it isnt a problem tho if it does start to cause you problems take it to a good guitar shop where it can probably be replaced quite cheaply
I sat next to a nun on the bus once, she said hi

Twitter: @Pikey_P - wise words right there.
#3
Do you mean the saddle? Are your strings wearing it down? If so, the wear could start to affect your intonation. Getting a new saddle isn't a big deal. If in doubt, take it to a repair shop and have the luthier take a look.
#4
The part that's chipping away is called the bridge saddle. It's removable from the guitar so can be replaced easily. I'd suggest that you do this, and install a bone replacement saddle. They are pretty inexpensive. I bought one recently for less than $10US. I did have to fashion it to fit myself, but there's tutorials on the net to help you with this.
For future reference, a little bit of lube goes a long way to help prevent this sort of thing from happening. I use Big Bends Nut Sauce. It's a special vaseline like lubricant with graphite in it that I use on the nut slots and on the saddle, and on the metal saddles of my electrics. The strings are metal, so they should be lubricated at those contact points. It really helps when tuning up new strings too.