X Software Engineer Intern interview questions

I conducted an initial phone interview with a Twitter engineer via the Kleiner Perkins Caufield & Byers program. I interacted with two HR people via email before the phone interview. The interview lasted about 30 minutes, and he only asked one technical question: implement the "getElementsByClassName" function using a simplified model of the DOM. This was based on my stated preference for front-end engineering. I went with a recursive solution to the problem, and after a couple minutes had it working most of the way. We talked about improvements to be made, such as a non-recursive algorithm, that would improve it's efficiency. Then I asked a few questions about Twitter. I thought the question went reasonably well as I answered it correctly, but was surprised about the lack of other technical questions. He said I would get a followup within three days, but eventually I contacted the HR person to ask about the status of my application and got a rejection email very soon after with little explanation.