The easiest way to get a group photo in which nobody is blinking is to take a lot of shots; but how many?
For groups of less than 20: divide the number of people by three if there’s good light, and two if the light’s bad.
Once there’s around fifty people, even in good light, you can kiss your hopes of an unspoilt photo goodbye.
It’s not quite that bad for large groups: you could always cheat with PhotoShop or Group Shot. For smaller groups, however, dividing by three or two is pretty easy — and with 16GB cards available and 4GB cards cheap you can easily afford to shoot five at a time. That’s good for ten to fifteen people, depending on the lighting, and probably about as much as your camera can do in one burst without slowing down.
For those of you with science or geek backgrounds, I thoroughly recommend having a listen to the Oct 14 Science Show. The recordings of the Ig Nobel prize ceremony are a hoot.