They did, last season, find a bar somewhere in New England to be not haunted in an episode that drew some scorn for how TAPS seemed to perform a lax investigation … the point, however, highlights one of my biggest pet peeves about GH — to investigate a commercial location that you have financial ties to (in the form of hosting tours and forums at said location) as TAPS does, not only makes the investigation dubious at best, it is totally, completely, unquestionably, UNETHICAL!!!
It's something to remember when Jay and Grant get on their high horse about how they don't charge for investigations, and when they present "evidence" from such locations.