Recently I joined Google plus, already using gmail and other Google services.
I must say it has become a bit of an addiction, posting messages or photos or reading and viewing other's in various circles I have created or added ('photographers', 'writers', or just funny and interesting people), from people all over the world whom I didn't know before.
To stay in touch with local friends and family I prefer to use my Facebook account.
New social media services come and go. One time it is 'hip' to be one of them, then they become less favorable and everybody is moving to other places to connect.
I'm going to stick to the two afore mentioned, unless they become invaded by a mass of advertisements or other commercialisation.