I don't sign in to my MySpace often but I do have my Youtube connection connected to my MySpace account. Any time I upload a video it automatically is posted to my MySpace account. Having my Youtube channel connected to my MySpace account helps my videos go viral without me having to manually upload my video to it.
Of course I use Linkedin, Twitter, Google + 1 and Facebook. If any of them offer me an opportunity to connect social networks to each other I do it because each time I post or upload a video my post and videos are automatically posted to help go viral.