Anyone have much experience with installing stone veneer?

I have read that people do or recommend installing the fake or real veneer “stone” from the top down.  It is supposed to make teh chance of getting motar on the stone below less of a risk.  I get it, but Is that a real problem?  Do people do it that way? Is it harder to get a natural look doing it that way as it is logical when stacking stone form teh bottom up to stagger teh joints, but might be a bit of a weird thought process to do it top to bottom.

Thoughts?