Say you got a letter from an advertiser, congratulating you on turning 30. It's unnerving: You've never heard of the company, nor where to even begin tracking down how they know your name, your address, and your birthday.

A proposed California law aims to change that.

Enter the Right to Know Act, which would give Californians the right to demand companies share what information they have on individuals and which companies they've shared that data with.

In theory, that would allow you to trace how you got that letter. You'd learn you put your birthday into Facebook, then authorized a third-party app to view that info without even realizing it.

That app maker's company then sold your name and birthday to a data mining company, which paired it with your likely address from an online retailer that shipped you goods, and sold that packaged deal to an advertiser.

Boom. Instant creeptown.

Authored by Assemblymember Bonnie Lowenthal (D-Long Beach), the bill is fairly straightforward, requiring "any business that has a customer’s personal information" to:

provide at no charge, within 30 days of the customer’s specified request, a copy of that information to the customer as well as the names and contact information for all 3rd parties with which the business has shared the information during the previous 12 months, regardless of any business relationship with the customer

The bill is being hailed by groups like the ACLU and EFF, which notes, "Californians do not want their personal information to be collected, bought or sold without their knowledge and consent."

If you are one of those Californians, the EFF has created an easy widget to contact your representatives.

Photo via Wikimedia Commons