I've used them.
So have I. At the IETF 71 IRTF ASRG session, a bunch of people who I
didn't know volunteered to do stuff, and without the addresses from
the blue (well, pink) sheets, it would have been a challenge to track
them all down.
I also get the impression that the fear of getting spammed is some
combination of anecdotal and ancient, since it's rather unlikely
that anyone is stealing them in the meeting rooms.
John Levine, johnl(_at_)iecc(_dot_)com, Primary Perpetrator of "The Internet
Information Superhighwayman wanna-be, http://www.johnlevine.com, ex-Mayor
"More Wiener schnitzel, please", said Tom, revealingly.
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