Good column, Robert.  I'm not sure I'd go so far as to call Wal-Mart a monopsony (or a monopoly).  It still faces competition from Target and, to a lesser extent, K-Mart (which I believe is now owned by Sears).  It will also likely face stiff competition as new companies enter the market in the coming years.  But something I've picked up on in my own experience is that Target seems to be grabbing for a slightly higher-end market, while Wal-Mart concentrates, obviously, on the lower end.

K-Mart is, in all likelihood, doomed.  It's in direct competition with Wal-Mart, and, honestly, it's not much of a competition.  Both are terrible stores that sell garbage, but K-Marts, in my area, are in such poor condition that it seems to be only a matter of time before they shut down.

There's a similar fight going on between grocery chains, at least in the South.  Winn-Dixie is getting smashed by Publix and Albertson's.  Publix dominates the Florida/South-Georgia market in a way similar to Wal-Mart.  People will, literally, drive past a Winn-Dixie to go to a Publix.

Anyway, I wouldn't worry about Wal-Mart's market power.  There was a time when a company called A&P -- I think it was A&P -- dominated the market and eventually crumbled.  Someone will build a better mousetrap.  It's not a market that lends itself well to being dominated by a single firm.  Microsoft, for example, has far greater control over the operating system market than Wal-Mart has in retail.  Wal-Mart receives too much attention.

Be nice to America. Or we'll bring democracy to your country.