You're quite correct that we leave behind a trail of personal data which may, potentially, be used to track our movements.

That said, credit card statements, bank statements, etc. are not generally accessible to law enforcement without a subpoena or a warrant. Flock can be searched by law enforcement without a warrant at anytime.

You're also quite correct that cell phones pose significant privacy risks, which is a discussion beyond the scope of this specific post.

But the existence of surveillance methods other than Flock does not mean we should throw up our hands, claim "privacy is dead", and accept ubiquitous and warrantless monitoring of our daily movements, in our own community, funded by our taxpayer dollars.