If someone has a pic on their profile that I like, and I want to use it as my MAIN profile pic, I FIRST ask them if it is OK to copy the pic from their profile. BUT here is the difference. I let them know that I plan on using that particular pic as my profile pic. That way, there are no surprises, when they happen to see that particular pic in my profile. Hope this solves part of the problem some may be having with stolen/borrowed profile pics...