Ok, I usually don't write about video other than commenting on YouTube because (a) I'm inherently biased and (b) I don't want my opinions to be taken as representing the view of my company. But.... since there's so much heat around the question of "Instagram for video" right now, here's a quick thought on why photos and videos are very different.
Think about the photos you look at in either your social feeds or specific photos sites: 99% of them interest you because the subject(s) and/or camera holder is someone you know (or you yourself). Because pictures are static, you can also grok and scan them very quickly, meaning the "cost" of a bad picture is low, hence you are interested in pictures from a wider variety of friends. The other 1% of pictures are not interesting to you because of the subject matter (flowers! eagles! antique doorknobs!). Various products are changing this split but I really don't think it gets past 90/10. [Of course there are photo buffs who just love to spend hours on Flickr browsing hashtags but that's not what's driving Socialcam and Viddy installs. And I'm not talking about photos which are incidentally included in news stories - eg the Tebow picture you see when you go to espn.com]
Now, about videos. It's the other way around. In 99% of the videos you watch you don't know anyone in the frame. You watch because the subject is interesting (and if it isn't, you bail pretty quickly). Why? Because there's a much higher cost to watching a video. Of course hours of video are consumed every day, so I'm not saying people won't watch videos, I'm saying the "social" in video is more about the subject and then sharing or discussing it with friends. Think of it this way, the average video has ~24 frames per second, each of those is a "picture" - i don't mind seeing a single picture of my friend and his baby in my Facebook stream, but I wouldn't want several thousand in a sequential slideshow. That's what a video is. Again, various technology and products are moving this from 1/99 --> 10/90 but I don't believe this fundamentally means I want to see more personal video from a broader range of friends.
Note: at mobile scale, 10% of the "video" market is still HUGE so I'm not saying that any of these apps are necessarily flashes in the pan. I don't know how to explain their recent spike, although I believe it has much more to do with Facebook distribution/feed changes than an inherently viral nature of personal mobile video creation or in-product network effects.
Off the cuff thoughts - where am I wrong?