Very interesting !! Some of the persons could get a little better, like the tumblr guy, the facebook dude and the twitter girl. What disturbs me a little is the head shape. And the (from characters view) right eye of twitter girl is a little to high. It shouldnt be highter than the left one, when she is looking down.

I like the coloring of Instagram lady. These orange outlines give it something special and fits nicely. I also like Snapchat girl and youtube boy. And the look of tumblr guy. Ok... when its just about the look, facebook dude is the only one I dont really like. Even if I like the colored outlines again, same with youtube boy.

Allover the single drawings could be a little better, but I really like the idea. (^.~)