Sometimes the products of acquired companies fade away, but that's not happening with Instagram, bought by Facebook for $1 billion last summer. "Instagram has a greater pull than Twitter on mobile devices" says the latest Comscore report, according to Fast Company.
Problem for Twitter, with their current developer program, they're shutting down Instagram's photo sharing competitors. Which means there will be little opportunity for a challenger to rise, giving Twitter something to acquire -- assuming their own photo sharing service fails to topple Instagram. Which clearly is not what's happening.