Its true that measures can be put in place to at least notify users when user-generated data hasn't been updated for awhile, but that doesn't do anything for the reliability/integrity of the database.
The perfect balance is probably to have user submissions which are moderated by a/some paid individual(s) and verified promptly by contacting confirmed airfield owners/managers. Then, the problem becomes one of covering the overheads... The sad story is that it would take a tremendous amount of work to make the ultimate database, but until it is "complete" and "proved reliable", no one would be willing to pay for it since you can already get incomplete and unproved information online for nothing.