Rainbow colour looks a bit cheap imo - for Google, because all its services are free for consumers, it plays fine.
If I'm starting a social media company though, I probably wouldn't want to venture out too far away from blue - simply because it's the easiest way for users to associate it as a mainstream social media company, i.e. alongside the Facebook-Twitter-Linkedin-Foursquare league, unless you are competing head on with any of these big four. I know this is a cheap strategy, but it also makes it cheaper for you to establish yourself in the market.
Or, just pick your favorite color, much easier and you'll always be comfortable with.
If I'm starting a social media company though, I probably wouldn't want to venture out too far away from blue - simply because it's the easiest way for users to associate it as a mainstream social media company, i.e. alongside the Facebook-Twitter-Linkedin-Foursquare league, unless you are competing head on with any of these big four. I know this is a cheap strategy, but it also makes it cheaper for you to establish yourself in the market.
Or, just pick your favorite color, much easier and you'll always be comfortable with.