My wife and I have done about 180,000 miles back and forth across the country staying mostly in Walmart lots hundreds of times over 16 years. We have been booted exactly once in all that time, from Homestead, Fl. Their security guard apologized and gave us directions to a nearby Publix that allowed overnight parking.
One other time a Las Vegas area Walmart security guard suggested that we move to a different store ten miles away because his store "had a lot of crime".
We love Walmart!!