Among experienced conrunners, it's generally agreed that the member's name should be in at least 24-point type, but a surprising number of conventions produce badges which fail at one or the other of these tasks, most commonly by neglect that negect to put the member's name on the badge or by putting it in 6-point type so that others can learn a stranger's name only by means of quite inappropriate familiarity.
The recent practice of some cons of issuing long lanyards for the badges rather than pins or clips also contributes to this problem, as the badges either flip over so the names aren't visible, or hang at a height that can make someone misconstrue where another fan's interest lies. (If it seems as if other people are staring at your potbelly or your breasts, try tying a knot in the lanyard to cinch your badge up higher.)
In the early days, badges tended to be simple pieces of paper inserted into a plastic holder, but more recently, they have become laminated, full-color pieces of art. This transition began at MidAmeriCon, whose organizers feared that that their then unheard-of high-at-the-door membership fee ($50!) might lead to forgeries.
Conventions also once commonly printed members' hometowns on their badges, which was a useful conversation starter, and often led to meetings of fans from the same area previously unknown to each other. For example, such meetings led to the founding of the Stilyagi Air Corps. However, this practice has, regrettably, become controversial, due to some congoers' privacy concerns.
The popular phrase "we don't need no stinking badges" comes from the film Treasure of the Sierra Madre