> If you don't want yours to be used, just buy another tracker from the tons out there.

I've already done this. But that doesn't mean I can't call out potential privacy violations in other products.

> Also I'd rather have my data harvested for science and medicine than for selling advertisements or whatnot

Can you prove this? Even if Fitbit isn't doing this now, what if they're acquired tomorrow by a company with more relaxed morals on what is permissible to do with health data?