I think the reason why it is a common misconception is because it works. Thin tires in snow just suck, they slide, they don't get traction. A set of tires with an open pattern like continental town and countrys is good.

I think 25c is best for less than a couple of inches of snow- it cuts thru and sheds slop quickly. On really icy packed or deep stuff, anyting without studs is going to slide a little. Knobbies stink.

Agreed. I've biked through 5 Minnesota winters without thin tires. Most of the time I'm not riding through deep snow, anyhow, since the streets here get plowed within hours of (and throughout) a heavy snowfall. I've also never had any need for studded tires.

When you get multiple layers of packed ice, with powder snow on top studded tires are ace. A good combo is a 28 studded ice tire with 25 cyclocross rear, both nokian (other cycloX tires just flat out way too quickly, IMHO)