Is rusting brake pads and rotors common?

What is your question?

I have a 2007 Jeep Liberty with 38,000 miles on it. I found out today that all 4 of the brake pads and rotors are excessively rusted out and needs to be replaced. This is, according to them, because I do not drive it alot (is an avg. of 170 miles a week not considered alot?) and the salt used on the roads in Michigan. I have a hard time believing this. To me, it sounds like faulty parts. BTW, the Lower controller arms on the rear suspension was just recalled today for excessive rusting out and causing accidents. Please help