From an AP standpoint, my spidey senses tingle every time I see a price match being attempted by a guest.
"Misplaced product (aka YOU HAD THIS ITEM IN THE WRONG PLACE ON THE SHELF AND NOW I WANT IT CHEEEAAAAP)," fake coupons, fake Cartwheel, trying to get prices matched from Ebay or Craigslist... the possibilities are endless!
I believe that people are less likely to try this crap if there's extra effort involved (you have to go to Guest Services, sorry!). I feel like more people are going to abuse this if it's easier to price match, especially if they see new cashier TMs at the registers.