Google Scholar wants me to add areas of interest, photo, and co-authors. I understand why I may want to add the first two, but why add co-authors? All the publications already list the actual co-authors. Is it an attempt to turn the site into more of a social network? Is it an excuse for Google to spam them ("X added you as a co-author!")? What is the benefit for the profile owner?

For example, I have some papers with dozens of authors. Should I "upgrade" them to "co-authors"? I have no idea who some of these people are, but maybe the goal is to get as many as possible. On the other hand, if I don't add someone I actually know, will they be offended?