Chromium suddenly starts downloading a binary blob

Quite. The open source nature of Chromium helps here, too: it is really not hard to prove, even from a position of total unfamiliarity with the codebase, that that executable is only executed at all if the setting is on, no matter *what* it might do. So the frothing about howgoogle is no better than a rootkit vendor or the NSA from Falkvinge and similar commentators is unjustified and says more about the tendency of said commentators to see conspiracies everywhere rather than doing a few minutes of actual research than anything else.