No, I didn't say you can illegally park.
If the driver LEGALLY parks, but then goes to a neighboring business, they can technically be towed by most state's laws, provided that there is a sign saying that "Parking is for Customers Only".
This is true even if the business has been closed for hours.
While I understand business owners calling for cars to be towed when people park in their lot for substantial periods of time and use other businesses, I feel it should be illegal for tow truck companies to "lie in wait" and police this themselves. The law should require the business owner to call the tow truck company themselves, and for at least 15 minutes (or something like that) to pass in order to tow the person. There should never be "towing traps" where people are enticed to park in the lot of a neighboring business, and then towed as soon as they set foot off property.