For some people, giving out their social security number over the phone is not something they want to do. In these cases, it helps to deal with a local mortgage broker where the borrower can go into the office and apply in person. Checking out the company's Better Business Bureau record is another way to alleviate this fear.

Your social security number and date of birth are needed in order for a mortgage professional to view your credit. There is no way he or she can look at it without it (together with your date of birth).
"But I know my scores" I hear you say, and that is fine.
You see, there is much more information on a credit report than just three scores generated by Transunion, Equifax and Experian. Your credit report lists how many active trade lines (credit cards, car loans, mortgages,student loans, etc.)you have. Many lenders insist on having at least five active (open) tradelines.
It is important to know what bills you currently have because a mortgage professional will always need to calulate your debt-to-income ratio ("d.t.i")to determine what you qualify for. For instance,it may well be the case that you simply wish to refinance your existing loan to a different loan program but not pay off any of your other debts. If, however, your debt-to-income ratio is too high to qualify the mortgage professional will be in a position to advise you on steps you can take so that you do. This might involve you paying off the debt from your own funds or paying off the debt through the loan itself.
Sometimes there will be information on your credit report that is inaccurate. By being able to review your credit report with you the mortgage professional can advise you on steps that can be taken in order to get those items removed from your report. This might even raise your score and allow you to qualify for an even better loan!
In summary:Mortgage professionals do not ask you for your Social Security number because they are being nosey. Your credit is a key factor in determining what loan program you can get approved for. Without it is is impossible to make an accurate assesment of your situation much less a realistic idea of your rate or payment.