Seattle ? Ever get one of those e-mails purporting that Starbucks doesn’t support U.S. soldiers, or that Coca-Cola has randomly chosen you for a cash prize? How about the tale that there’s pig fat in McDonald’s soft-serve ice cream?

Rumors fly fast and die hard in the world of e-mails and blogs, creating a dilemma for some corporations that face the never-ending task of setting the record straight.

Many have rumor-response pages on their Web sites and monitor what is said about them on sites like Snopes.com and Wikipedia.com. Despite those efforts, the same myths and untruths can circulate for years.

“Once it’s on the Web, it’s like taking the rods out of a reactor,” said Chris Gidez, head of U.S. crisis management for the public-relations firm Hill & Knowlton.

The same medium that spreads rumors can be a gauge of how far and damaging they have become. Most big companies spend a chunk of time watching blogs, message boards and other sites for rumors and to see what people are saying.

Companies that are subject to lots of rumors should respond to important ones, said David Dunne, general manager of interactive solutions for the public-relations firm Edelman.

But software companies often use their Web sites to address every virus rumor, he said, because “it’s important to tell the people who use their software not to worry.”

More traditional businesses have picked up the habit, too. Coca-Cola’s Web site addresses so many rumors that they are categorized into separate myths and rumors pages – one for rumors from the Middle East, another for products and packaging, and a third addressing contests and promotions.

For the Atlanta soft-drink company, it is more important to address rumors than to try to contain them, she said.

“When unfounded statements are repeated often enough,” said spokeswoman Kerry Kerr, “they do start to cloud the truth.”

In trying to kill a rumor, companies often enlist help from outside sources, including linking to other Web sites like Snopes.com, a well-regarded reference for sorting out myths and rumors.

Starbucks went directly to the source of one of its most virulent rumors, which says the company doesn’t support the war in Iraq or anyone in it.

That tale began with an e-mail from a Marine sergeant in 2003 or 2004, who wrote to friends that Starbucks had said so in a letter to Marines in Iraq who had asked for free coffee.

Several months later, the same sergeant wrote another e-mail apologizing and saying he was mistaken. Still, the rumor has not died.

“We get it every few weeks,” said Starbucks spokeswoman Valerie O’Neil.

McDonald’s does not have a rumor-response page for U.S. customers, but its Australian business has a site called www.MakeUpYourOwnMind.com.au that addresses whether its soft-serve ice cream has pig fat.

“There is definitely no lard or pig fat,” the site says, “in the McDonald’s Soft Serve.”