I don't doubt for a second that previous posters have seen cars towed from resort lots, but the chances they were towed for going to a park are slim. More likely, the towing was for mechanical problems or parking in a fire lane, service area or other clear violations.
Florida law is very specific and highly restrictive when it comes to towing vehicles from private property and at present WDW resorts don't meet the requirements.
Disney has every right to deny parking to anyone, but once they've allowed someone in, they can't just start towing cars at random.
I wanted to clarify this so that people with legitimate business at a resort - dining, shopping, etc - aren't filled with angst about getting towed.