When your deed is filed in the county office of records, it include information about any liens on the property. The lien info include the lender's name, the sales price of the house and frequently a bunch of other information.

If you ever refinance it changes the lien information and you'll get a whole new pile of offers.

The funny thing for me is half the time they advertize a low (varible) interest rate, that starts higher than my 10 year fixed rate home loan.