Linking and Lag

I've heard that prims which touch and/or overlap create more work for sim and/or client than if they're not touching. Is this true? If so, what is the reason, and does linking them reduce or eliminate the problem? How close do prims have to be, to be considered touching?

I never heard this regarding normal prims. It's true for physical prims though, for obvious reasons.

Seconded.

I can't imagine non-physical touching prims causing more lag.

Perhaps if they're using a collision event of any sort in a script, but otherwise it shouldn't at all. A lot of builds (Hell, almost all of them) have overlapping prims, in various places and quantities, and I've never noticed any more lag someplace that seemed to have more 'intersections' or anything.

If there is more lag, it's quite minimal, I assure you.