As a counterargument, even if you use Gmail (or any other email provider) there's nothing to stop you from using another provider and continuing to communicate

As a counterargument, even if you use Gmail (or any other email provider) there's nothing to stop you from using another provider and continuing to communicate with any other user via email. But if you like Google+ more than Facebook for sharing messages, links, and pictures with friends and family, how do you do so if they're all only on Facebook? (Obviously this works either way). The bit that really disappoints or bugs me is how something like email is still generally interoperable between providers so each individual user can pick whatever provider appeals to them, or even host their own. With closed social networks, you essentially must have an account on a given service in order to use them. If you want to use a different provider due to personal preference or some feature offered by one and not another, you either have to convince all of your contacts to switch over or accept that it's not happening. At least with AOL email or whatever you could start using Yahoo or Hotmail or Gmail and continue to send messages to your mom and your boss and your doctor's office even if they stubbornly clung to AOL. Today, when better social networking services and applications come out, you can try them out but (as Google+ showed) they become pretty sparse when a majority of users are happy to stay with what they know and there's no way you'll get most to consider using a different service.