I wouldn't be surprised if there were ordinances in place to discourage/prohibit...

poopsintub · on Sept 9, 2014

It seems like every Wal-Mart has a sign now for this. I imagine their big empty parking lots might have received decent use a few years back.

maxerickson · on Sept 9, 2014

While we do not offer electrical service or accommodations typically necessary for RV customers, Walmart values RV travelers and considers them among our best customers. Consequently, we do permit RV parking on our store parking lots as we are able. Permission to park is extended by individual store managers, based on availability of parking space and local laws. Please contact management in each store to ensure accommodations before parking your RV

from: http://corporate.walmart.com/frequently-asked-questions