That's the case for some, but (1) most applications that lean that way are likely to be closed source as there is a certain sense of apparent moral high ground that comes with open sourcing and (2) more importantly Mozilla sells themselves on respecting privacy, first and foremost.

> I now fully expect the cost of entrance for free applications to be data the developers collect of my usage.

Apparently this is also true of applications & services you pay for these days too. Includes ISPs, cell companies, cable apps where you input your customer code, paid subscriptions to online news... the list is endless.