Commercial privacy online is just about out the window (you'd be amazed at how many organizations track your online history), but as this has become the new normal, most people have accepted it.
Take a look at this hypothetical PowerPoint deck about a future of law enforcement, though. It will certainly make you think about how far you want this to go.
And then consider signing this petition (deadline is today) to demand a public policy stand on warrantless snooping.
I don't think there's a clear and obvious line that everyone ought to agree on. It's clear, though, that the time to have a public discussion is now, as later is certainly too late.