We went around to several Walmarts while in Alaska to check out the camping status. The only one that was a problem was downtown Anchorage. They had no parking signs posted. I talked to some local campers in the lot and they said the city posted the signs because of complaints from the campground owners. Sound familiar? Some said they had stayed one night and didn't have a problem but it is touchey. There really is no need to worry about it anyway. Just up the road a few miles is the old K Mart Supercenter which is now closed and it looked like a campground. Sams club is right across the street. I have pictures. The city doesn't have signs on this lot. DUH. Anyway the new Walmart is in a real crowded area right off the old GlennAllen Hiway, which doesn't really have room for parking, so I am sure that is why they are trying to discourage it. RV parking is real friendly anywhere on the sides of the roads where there is room ( outside the main city, Anchorage, and we saw lots of people grouped together in the evenings (3 or 4 rigs) with their tables and chairs out eating and uh you know. I am sure they were this way because there is safety in numbers and they felt comfortable doing so.
Check it out.