You can sell your company and still retain an ownership interest. If you owned a company and data access was critical to profitability then Facebook has a lot

You can sell your company and still retain an ownership interest. If you owned a company and data access was critical to profitability then Facebook has a lot of leverage to "encourage" you to sell: you can either own 100% of the company without access to the data or own 10% of the company (or whatever percent Zuckerberg was generous enough to allow you to retain) with access to the data.