In this case? Security as theater. Most Americans, if they see something they feel is suspicious or people who look dangerous, will report that to a security guard or police officer. They don't need this at all. Ergo -- theater.

Do we need to be paranoid yet? (About this? Probably not. Otherwise? Heck, yes....)

Some links:

1. Walmart Partners with U.S. Department of Homeland Security ...

"6 Dec 2010 ... Everyone has a role to play in keeping themselves
and their communities safe."
walmartstores.com/pressroom/news/10493.aspx

2. Wal-Mart joins Homeland Security terror fight - U.S. news ...

"7 Dec 2010 ... To expand its anti-terrorism campaign, the U.S.
Department of Homeland Security has partnered with Wal-Mart,
bringing its 'If You See ..."
www.msnbc.msn.com/id/40552073/ns/us_news-security/

3. Walmart Shoppers: Homeland Security Wants You : NPR

"11 Dec 2010 ... Starting this week, Walmart shoppers will be
treated to a short video from Homeland Security chief Janet
Napolitano, urging them to report ..."
www.npr.org/2010/12/11/131991345/wal-mart-shoppers-homeland-security-wants-you