G'day AMRAAM,
We spend a few hours each month going over each Avdata account against the aircraft flight logs. Whenever we find an error, we just take it off the account with an explanation ie, "Aircraft *** was did not go to that airport on that day".
We've never had "threats" made against us for refusing to pay a disputed landing fee. In fact I'd suggest that in any legal procedings to recover monies own the burden of proof would lie with Avdata to prove that the aircraft actually landed at that airfield rather than the pilot or owner proving that they didn't. Given the countless cases of proven fraud and erroneous Avdata readings I don't think they'd stand a chance short of having a reliable eye witness on the ground at the time to back their voice tapes.
The concept of aerodrome operators collecting fees to recover some of their maintenance and upgrade costs is fair enough. Unfortunately though through the appalling lack of integrity by a good number of pilots, what should be a straight forward method to achieve this has turned into a farce for all. Short of the councils etc employing someone to sit all day and night at airfields recording aircraft regos there doesn't seem to be an easy solution.