IEEE 802.11 / 802.15 meetings have solved this by attaching a helium
ballon to their equivalent of the blue sheets. That way everyone can
see where they are and if they have gotten hung up.
That's a fun solution to the more general problem of slow blue-sheet
propagation. For the name harvesting attack, my favorite idea
(perhaps for no better reason than because its mine) is peel-off
numbered (or bar-coded) labels on the backs of the badges, to be
affixed to the blue sheet. The secretariat, of course, would have
the number-to-name mapping.