I had this happen to me. Granted, they got me before 16 months...more like 4 months, I think, despite my diligent efforts not to fill out ANYTHING marketing-related during my pregnancy.
I called the company, sat through their *GAG ME* Formula ads on hold until I got to a person. I told her that I had just received a can of formula in the mail and that I planned to dump it into the toilet, as that was the best place for it. However, before I did that, I'd like to know where they got my address and why they thought my healthy, exclusively breastfed 4-month-old needed formula. She got very pissy and said something like "you could give it to someone who needs it..." I made it clear that would NOT be happening. She eventually said that my name appeared to have come from "a doctor." I asked which and she said she couldn't tell me. I said that I'd used a midwife during my pregnancy and I could only assume it was my pedi. I told her to inform her "source" that they are in violation of confidentiality laws and REMOVE MY NAME FROM HER LIST. I never got anything else from them.
Then I called the ped's office and spoke with the nurse, the office manager and the doctor, all of which assured me that they are NOT selling names to formula companies and that if my name came from their office, it was through illegal means and they would look into it.
So I don't know how or where they got my name, but the surely don't have it anymore.
BTW, I think this was enfamil.
eta: it occurred to me later that if she wanted me to give it someone who needed it, I should have asked why in the world they sent it to me in the first place as I obviously don't need it. It eventually got thrown away, as I had no desire to donate it.