Boot, I design & build large custom homes & have ALOT of dealings with realtors.
As I understand it, it is highly illegal to tell someone there is another bid if one doesn't exist.
If someone really is trying to "up" the ante, they are risking loosing their license as well as a few yrs behind bars.
If it was a boat broker, I could see it happening but in realestate, I highly doubt it.
Good luck to you