Actually spoofing ADSB radio signals could very well land you in prison with a $100,000 fine. The FCC is very eager to find and fine you for these kinds of stunts.

Spamming flightaware is much less severe, but still... it's not cute to mess with life-safety critical infrastructure.

FlightAware isn't safety critical. If it was then being able to spoof it in this manner would be negligence on the part of the operator.