A small thing from the last time I went to Wal-Mart. I was spending a fairly significant amount of money (about $200.00, including electronics). I went through the checkout line of an older woman. I greeted her 'Hello,' but she said nothing to me; placing all my expensive purchases on her conveyor belt, she continued to say nothing to me. I paid by credit card (apparently, the credit card machines now ask if the checkout person has greeted you... No.) and she handed me my receipt. No 'thank you,' no 'have a nice day,' no nothing. I made sure to tell her to have a nice day. :)
Now, I'm sure it sucks to work at Wal-Mart, having to stand on one's feet all day long, dealing with annoying customers, and making low wages. I work in customer service, so I know how difficult it can be to be nice and to be happy all day long. But, I expect a small modicum of customer service from a person who deals with people (just a small hello or thank you).