The LFGSS family photo

"http://www1.istockphoto.com/file_thumbview_approve/3615573/2/istockphoto_3615573_transparency_film_frames.jpg"

if you used a shift lens on a 12-16mp camera (like the 90mm i have for my canon) you could in theory get a near 30mpixel image but you would get problems stitching because of people moving and the time it takes to shift.
CS3 has a really good auto stitching feature so if you quickly shot a left/center/right frame it would join seamlessly and deal with any parallax errors (as long as people didn't move too much)

Where you position the camera on the tripod with regard to the pivot point should address any parallax problems shouldn't it ? By that I mean you can set it up so parallax is not an issue to be resolved in post (I could be wrong here ???).

Anyhow, it will never be perfect, people will always move or start talking to the person next to them, so fuck it, the picture would be as good as it is.

[Edit]I might not have go the right idea with your 'shift lens' I was just thinking of panning the camera through three separate exposures ??