I used to cringe when the guy I least wanted to get to know would ask for my phone number. That's exactly how I feel now when a company insists on getting my Social Security number before I do business with them.

Many people who raced to buy the iPhone last month had a similar reaction when they tried to activate their AT&T wireless service through iTunes' Web site and were asked to provide Social Security numbers. The issue has been a hot topic for bloggers on news.com, magpiebrain.com, iconnectdots.com and other Web sites.

AT&T spokeswoman Susan McCain defended the practice as a standard request for monthly service plans. The company uses the information to perform a credit check.

AT&T is hardly unique. Schools, utilities, health clubs, credit bureaus, insurance companies, video stores -- just about everybody, it seems --wants your Social Security number.

At the same time, consumer advocacy groups and government agencies are telling people to limit the use of their number.

What are we to do?

When I was younger, my friends and I would simply give the guy the wrong telephone number and hope to never see him again.

But that tactic won't work with your Social Security number, because intentionally giving a false number is illegal, said Kia Green, a spokeswoman for the Social Security Administration.

"It's a federal law, which makes it a felony punishable by up to five years in prison and a fine," she said.

The Social Security number was established in 1935 for the purpose of tracking earnings and paying retirement benefits. Green said Congress has since expanded its use.

There are a few organizations that have the right to demand it, Green said. They include the federal and state revenue departments, state motor vehicle divisions, and social service agencies that oversee food stamps, child support, Medicare and Medicaid.

As for all those others that want it?

"You have the right to refuse to provide your Social Security number, but the business has the right to refuse you service," Green said.

If you are insistent about not providing your number, some companies will try to accommodate you. The key is to be firm, but not hostile.

For example, when I called AT&T a second time, another spokeswoman, Della Bowling, said that if a customer insisted on not providing his or her Social Security number, the company would accept a deposit instead.

There are a number of tactics you can try to help guard your Social Security number. Some examples include:

* When completing an application, leave the line for your Social Security number blank. It's possible no one will question it.

* Talk to someone higher up in the organization about what other information might be acceptable.

* Ask why the number is needed and insist on seeing the company policy requiring it.

* Say you will take your business elsewhere, and follow through.

* Ask how the information is used and about safeguards the company has in place. Ask whether it accepts any liability if the number is stolen.