The only thing about fads changing is, don't people get sick of re-following their friends every time a new app or website comes out?
And for me, Instagram and Snapchat (although this seems like it will be a very short fad) are on top, but I only used Tumblr in 2010/11 and got so bored with it so fast so I'm not going back there.

I still use Facebook but it's so stupid now.