Yes I just noticed that too.
Stopped getting alerts one day after making them.
Stalkers… 
well not me if that’s what you meant. 
Maybe of course with someone of his fame but, but probably he just didn’t want people to know every vacation he took. Who would?
also I’ll bet most aircraft registers will start automatically blocking n numbers for their clients just as a matter of course which unfortunately will make the whole system worthless.
If you are an aircraft fan then its things like the n707jt that you want to see land.
The more exotic aircraft will be owned by interesting people who will want blocking.
An also if the data set isn’t complete then it makes it hard to use the data for aircraft pattern analysis and traffic analysis etc.
Unfortunate.
Have I ever shared my feelings about blocking aircraft tracking?
Yesssss 
… And you know my position too Mister… 
not to me !
tell the new guy