In this article in really sounds like Catherina Fake regrets her decision of selling Flickr. It must be a very hard decision : accept 40 M$ or keep growing very personal work.

What I found interesing is that she underlines the fact that Flickr has been (is) very popular because of special circonstances, the fact that digital cameras began to be cheap and widespread, more and more people blogging...

It seems like Flickr became successful in a large part because of a lot of luck.