I was pleasantly surprised when I saw this email sitting in my inbox today. Flock was officially being shut down from April 26th 2011. The social interest in the niche browser had been dropping drastically and when Zynga acquired them for their developers in January, the end was almost sealed.
Personally, Flock was a neat idea. You got a firefox build (later chromium), which came with social features right out of the box. Sidebar access to twitter, facebook etc. Seamless access to your delicious bookmarks, email, blogging platforms..
Why did Flock fail?