I have been reviewing standards that show the benefits of using circular pictures. We recommended this option to a client but the developer raised concerns over cropping. The developer mention when clients want to crop pictures with other people it is problematic. Has anyone run into this concern from development? or other issues with cropping in circular? this seems like a strange concern but they convinced the client it was an issue.
It depends whether you want the user's profile to be their face or not.
On one hand, the client is right - it would be harder to fit a group photo into a circle, or many photos that aren't just faces. There's a reason camera's take rectangular pictures, after all. So if you want users to have profile pictures that aren't their face, than a square seems the natural option.
On many sites, though, I would imagine that you want to encourage users to put their face as their profile picture, because the purpose of the picture is to help users identify each-other. In this case, it makes sense to make the pictures round, as a way to encourage users to make their profiles their face.