Seems like a dangerous proposition to choose some airports as having the
concept of a voluntary controlled airspace?


What seems dangerous about it? TRSAs exist in Class D and Class E airspace
but are not in themselves controlled airspace.

Ah, that's where I made my mistake - thinking that it's controlled
airspace (as in Class B). I just remember my instructor telling me to
always participate when flying into a TRSA, but never really
understanding why it was voluntary in the first place. Thanks for all
the replies everyone!

--
Guy