I s'pose I'm coming purely from the view of a shop-owner here, but requiring the buyer to pa-ss all of the other items in a shop can benefit the owner, and sometimes quite a bit, too. It's like a little kid at Wal-Mart; his mom is just there to buy groceries, but the moment they walk by the toys, 'Hey Mom! 8D' He has to get one.
So, sticking the item for which you're looking conveniently at the top may slow business a bit. I know I was certainly glad for it when someone once bought a few of my Mirabilis eggs while she was shopping, despite their being nowhere near the lowest price (since I really dislike undercutting on eggs). It pretty well made me wanna go buy something from someone else. And I did. Kinda led to forgetting about saving, and I went on a spending binge that day. x3 Got some tu flowing, eh?
A confirmation button would be nice as an optional thing. I do recall once when I'd only been here for like, a month, I accidentally spent almost all my tu on an 'item' that didn't exist and had glitched itself into a few shops. I freaked out. xD
Lard, I ramble.