My BEST chain store is the B&N at Desert Ridge in Scottsdale. They've sold 300+ of my books this year alone, and I have my own endcap. I would drive through a blizzard (and have done so) if they asked me to. But, I'd always (as a shopper) preferred Borders. I try to be (as a shopper and an author) supportive of both, and do drop-in stock signings as frequently as I can, wherever in the country I happen to be.
On Christmas Eve, I was in Californina, in a city with a Borders and B&N in sight of each other. I signed stock in both.
At the Borders, I took the stock to the information desk to sign. The clerk asked, "Are you buying all those?" I replied, "No - I'm going to sign them."
She answered, "Then I hope you're going to put them back, too."
I said I would. I signed them, sketched in them, and asked for a manager, who found "signed by author" stickers for them. I reshelved the books and left. The clerk(s) could have cared less that the books were being signed, and were mostly complaining about the hours they'd been working. Fair enough - they didn't know I was coming in, and owed me nothing.
At the B&N, I found the books and started signing them. One of the clerks offered to look in the stockroom for more, and brought them out. Then she made (at my suggestion) an announcement that I was signing books in the children's section. That brought some interested people, and immediate sales. I kept signing. More announcements; more sales. Then, she introduced me to the CRM, who gave me his card and asked to set up a formal stock signing (with more books) the next time I came to town. And the clerk took the remaining books and set up a display in one of the center aisles.
I went back to both stores on the 26th. The Borders had sold one paperback. The B&N had sold almost every copy I'd signed. Ten bucks revenue versus several hundred, in two days.
There are probably a thousand factors I'm not taking into account here, but in this single example, I'm pretty sure the attitude of the employees had everything to do with it.