Duplicates: T28242
Importing any Collada scene from Sketchup 8 (I think it's not specific to sketchup but didn't see that problem with my other programs as they all produce meters .dae files) to Blender changes the unit system of the current scene. An imported object should respect user's chosen unit system not the other way round.
I can make an example scene at school if needed, but just doing a 2*2*2 cube in sketchup, exporting to collada is enough to see the bug.