This question seems to come up every now and then and it’s always curious looking at the answer. The thing about a lot of social networks is they didn’t start life in that way. If there is a new social network that emerges my feeling is it will be from something which started life as just another app that is useful and then has the social aspect added later. Think similar to Instagram (which was initially a photo filter app I believe). People don’t need another channel to connect with friends and family with. They need something that is useful or allows them to be creative. If it has a networking element then that will grow organically if the app is useful.