I offer this up as an example of upward sloping demand curve (see the discussion in Marginal Revolution.) Well, maybe just an upward sloping portion of some individual demand curves. According to this report, some consumers have stopped buying from Wal-Mart because they think its prices have dropped so low, they must be hiding some "unfair" business practices. (Is this Only In America? I wonder.) Most people shrug it off - see, their demand curves are downward sloping. (Why else is this a newsworthy report? Man bites dog, see.)
Wal-Mart critics rail against excessive "market power". Duh. Might as well condemn the consumer's "market power". Why does Wal-Mart drop its prices? Only to persuade consumers to buy more. In fact Wal-Mart is the silver bullet against another kind of market power - the anticompetitive practices of suppliers, other retailers, and organized labor. Maybe Wal-Mart should be up for a Trust-Buster award.
The price-tamping effect of Wal-Mart is confirmed by some recent research, cited in a Business Week article. I don't know about those upward-slopers, but give this normal consumer Wal-Mart-style pricing anytime.