As a plane geek I love Flightradar24, Flightaware, ABS-B Exchange, etc. I even host a receiver and share data to these sites.
But a war is brewing. Wealthy people's feathers are getting ruffled by this as they realize their private planes can be tracked pretty much anywhere. Often citing corporate espionage scenarios or just because I want to be anonymous (eg: stalking).
I understand the wish for privacy, but on the other hand you're using a taxpayer/public funded system. Even when out in our cars we know there's plate readers logging data...although no one seems to care enough to compile that data and share it on the internet (as far as I know anyway). Figure if you really want to travel under the radar your best bet is to take the bus using a fake name.
For the longest time everything in aviation has been public info. You can search a licensed pilot's name in the FAA database and get their address, ratings, and date of their last medical exam. Type in an N# for any plane and get all the info on it. Think these days are numbered?