To expand a bit on Driftwood's comments, which I strongly endorse;
Cutting back barrels;
1. Reduces resale value.
2, Reduces flexibility, as their usefullness for other purposes is also reduced.
3. As Driftwood says, choke can be affected.
4. Weight is reduced which may effect comfort when using heavy loads.
4A. See the post below by Pony Express. The lesser weight of the barrels of a sawdoff might not be enough to open some guns enough for a quick reload
5. Shortening barrels affects swing on flying targets, but mostly it causes OVERSHOOTING. On a shotgun "sights" are effected by the placement of the eye behind the gun (stock weld) and the front of the muzzle, and less prominently, the bead. If the barrels are shortened it changes the angle from the eye to the bead causing over shooting. The English gunmaker Churchill created his famous 25 inch barrelled guns only after he perfected a raised rib to counter the overshot effect. Further, errors in stock placement on the shoulder that happen when the action gets tense, most often create more overshooting and are magnified by the shorter sight radius.
Every time I write this, the list gets longer. Cutting barrels is the most misguided habit that has come out of cowboy action shooting. The pinnacle of my cowboy shooting career came with the use of 30 inch full choke barrels on a '97.
IF you want a barkeeps "Sawdoff", buy one as it comes from a factory as some of the negatives are neutralized by the maker.
I hope you forgive my STRIDENT TONE! But try to add that length of barrel back on when the regrets surface.