Once you've already called the big blind, calling a raise that came behind you doesn't qualify as cold calling. Cold calling is calling a raies before you've invested any money in the pot. If you've already limped into a pot and then someone raises, you should always call.

The reason you should cold call with some hands in late position only when 3 or 4 people have already entered the pot is because those hands play well multi-way. You generally wouldn't want to in early position because you can't be sure you will get the multi-way action the hands need.