I don't agree with the interface comment. Facebook became popular in part because it had a much cleaner, more usable, interface than MySpace. I think the same is true of Flickr, though I'm not a heavy user.
It's probably true that other, newer companies have created better interfaces since then, but I'd argue that they became popular because their interfaces were superior at the time.
> I think the same is true of Flickr, though I'm not a heavy user.
Might have been true in the past, but I'll be damned if I don't just insta-close any flickr link I click by mistake these days. I just want to see a picture and half the time I get these two dots swirling around for what seems like half an hour, until it leads me to a half-broken interface with a tiny dot of a picture.
Both Flickr and Facebook had awesome interfaces when they first became popular. They just didn’t change enough or went in the wrong direction afterwards.
Much the same with Google Plus. It takes serious effort for growth and the infinite strength of 'user needs' not to clobber a good interface with lots of cruft that most users don't want.
I think the Flickr UX is pretty good, but I've only been a user for a couple of months. So maybe the problem is that the Flickr UX can't grow with the user/photographer?
As for Flickr: isn't it strange how the products with the worst user interfaces always seem to become the most popular? Same with Facebook.