I haven't figured out why TFR's exist. How are they supposed to
protect the President and/or whatever else?

Yes, that's the general idea. Of course, what they really do is
protect the career of the bureaucrat who might otherwise have made the
decision to abolish them as unnecessary and perhaps hazardous to the
president's health. (Is it really smart to draw a circle around him
wherever he goes, the way my mouse does to the cursor when I'm trying
to find it?)

all the best -- Dan Ford
email: www.danford.net/letters.htm#9

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