I fly a lot in the US (Canadian pilot), and always file a flight plan. Question is - how do I know if I’m being tracked?
If you’re flying IFR and talking to center, you’re probably being tracked.
If you’re flying IFR and talking to local controllers, you’re possibly being tracked.
If you’re flying VFR, you’re not being tracked.
mduell forgot one scenario…
If you are a complete conspiracy theorist, you are always being tracked. Big Brother is watching you.
Depending on what you’re talking about, the most simple answer is that if your transponder indicates that it is being interrogated, you’re being tracked.
Thanks for the reply. I was actually referring to being tracked by an individual on the ground, in the same way I have a friend whose t-number I enjoy tracking. (And no, I’m not an aviation ‘stalker’! ) 
Is it possible to identify who it is who’s doing the tracking, and if so, request immediate anonymity? (Sorry to perhaps be asking the obvious, but I’m not sure just yet how that part of it works, even after reading the FAQ’s.)
All of these sorts of questions are covered in the FAQ. For example:
Can FlightAware track VFR flights? What about a VFR flight with a flight plan?
Can I block my aircraft on FlightAware?
As far as knowing what other users are doing on FlightAware, that’s covered by our privacy policy which, of course, doesn’t allow that.
OK, thanks, guys - maybe I should rephrase: is there any way of knowing exactly WHO (as in ‘name’) is tracking you? I know I’m being tracked by the Big Guys, which is great. No problem there. Just curious about the personal ident of the person behind the PC.
Hi – you might have overlooked this part of my reply:
Thanks - that’s all I wanted to know!
There is no way of knowing who is using FlightAware to track your plane at any given time. 
I suppose there might be internal log files kept on the FlightAware servers that FA staff could access that might be able to tell who queried a particular tail number. If such logs exist, then only FlightAware staff has access to that information and would be made available to law enforcement agencies through court order.
That answered my question exactly, and with more detail. Thanks!
What’s your tail number?