Rumors aren't confined to neighborhood gossip.
The biggest corporations in the world use rumors. Every day, rumors cause stock prices to rise and fall, competitors to start madly developing products -- or abandoning them.
Public officials, political campaigns and advocacy groups traffic in rumors to hurt rivals, kill legislation or advance an agenda.
Sports teams have made trades based on rumors.
Actors and directors have gotten jobs, and been fired from jobs, based on rumors.
It's instructive to see how public figures and corporations at the highest level deal with the constant threat of hearsay, gossip and rumors.
Corporate Rumors
Vaporware is a constant threat in high-tech business.
Say you're a tiny startup company in San Francisco, writing software that lets you take your Droid or iPhone and use it to control an army of robots who'll mow your lawn and take out the trash and obey your every command. You're about to go public and sell stock.
A giant such as Apple could squish you like a bug simply by planting the rumor that the next iPhone will include that feature automatically.
Your market is gone. Nobody will buy your stock when it goes public.
Can this sort of rumor be verified as true or untrue? Not really. The next iPhone may not come out for six months, and they naturally protect those secrets until there's a rollout.
Pre-emptive Rumors
You'll see the same thing in politics. A young politician may be planning to run for Congress, and a much more established rival, who has no plans to actually run for the same seat, could sabotage the campaign by planting the rumor that they'll run for the same seat.
Donors who may have written checks to the up-and-comer will wait to see if the political lion runs. Consultants and campaign staff will wait.
To Comment, or Not to Comment?
Many big corporations and public figures have a policy of never commenting on rumors.
This is typically smart, because rumors only get stronger when you feed them with attention.
A common mistake in combating rumors is to come on too strong when denying them. The press and public thinks thou doest protest too much.
However, this does suggest a defense against rumors from a competitor who tends to traffic in them quite often. You could turn rumors against the nasty people who use them by being seemingly random -- but strategic -- about when you ignore rumors and when you do protest too much.