I think Facebook has proven by now that even if they aren't doing this on purpose to trick advertisers into thinking their ads are much more effective than they

I think Facebook has proven by now that even if they aren't doing this on purpose to trick advertisers into thinking their ads are much more effective than they really are, at least the product doesn't seem ready for primetime with so many "bugs" in measuring popping up. If you're a small business, Facebook may screw you over big time, so it's not worth the risk. I assume big companies just don't care.