I always thought a fob was like a leash..something to hold something else.
Remember the ad's in comic books for squirrel monkeys they always came w/ a fob.
My wife bought a fob for me but it doesn't work, I'm a hard dog to keep on the porch lol.
I have seen some watch fobs go for big cash...I think one ot keep an eye out are "Harley Davidson" fobs, but basically anything that is no longer made or have a big following. Check EBAY for some of the prices they sell for...that will give you an idea on what is worth keeping en eye out for!
I think watch fobs are very nice finds and add to a collection nicely :-)