Sharing can be shrugged off as something irrelevant, but i look at in in a number of ways.

1) Free advertising for lesser known games. Remember those niche games you play that you wish your friends were into or could understand why you love them so much? If they see a gameplay clip that you have been playing, it might persuade them or provide them some interest. e.g. "wow that game looks great, I might pick it up".
2) Great for video commentary. I imagine there will be tools or a native app to remix your clips you record, so you can record your voice and combine the two and upload it.
3) Great for live streaming. It's well supported, easy to setup and your friends can know what you're playing at all times, and watch you play and comment.
4) The functionality seems to be in-obstructive, quick and simple.

However, just like I wouldn't want to be spammed with things I'm not interested in, I can see people getting irritated by constant game video sharing on their social networks. I hope a balance is found, but since people will be people, I don't have total confidence about that.

Cool feature...

Don't worry people only videos that are gona be showing up are your friends and if you have a dueche of a friend that posts videos of him staring aimlessly at a wall delete him problem solved. The way you need to look at this feature is let's say you are playin a game an your stuck at a certain part so you upload the video of where your stuck at and ask your friend that is playing the same game for help and he post a video for you showing how to complete that part of the game. Just a way I guess you can use it.