Ask HN: Who are the biggest names in the personal data processing industry?

Obviously, data is valuable. I'd like to pose this question to pool the entire HN knowledgebase to create a list of the biggest businesses that process personal data, directly and indirectly.

We obviously have companies with direct contact to the end user (via a product), like Facebook. But we also have the Ad Networks and other companies that are in the business of selling personal data.