Matt Cutts thinks he can improve the typical conference’s name badge. He breaks it down in this drawing:
2-Sided is a pretty good idea since they do tend to flip around.
However, Dan Grisby has proposed a different solution to the flipping problem that may work equally as well: Use two holes. If the badge has holes punched on each corner rather than a single hole in the middle, the spaced lanyard attachments would probably be enough to keep it from spinning.
Dan’s solution to that part of the badge problem seems like the way to go because few conferences are set up for 2-sided badge printing.