I think most of mine have been about 1½" wide for the measure of the bottom mat, although I think I've gotten a few as wide as 2" in the swaps I've done.
I know everyone's taste varies, but remember that there are some people who may be doing 8½x11 instead of 12x12 pages. (That's also the reason we ask for 12" that can be easily reduced to 11". Anything wider than that would overpower the smaller pages.