Some time ago I participated in some Startup Accelerator.
Was part of Startup with really fast growing user base, but small amount of sales. What some investors really suggested to do with our database - is to sell it!
So companies can sell personal data (and they do it) not only when put up for sale, but at any time.
https://31.media.tumblr.com/cd2e1b3c549cdec0918a2000892c6c07...