... "They use PHP on the front-end because it is easy to learn, easy to develop in and it is very productive. However there are downsides such as the fact that their benchmarks have shown that it is ten times slower than if they used more traditional web programming technologies like C# or Java. They have done a lot of work to optimize PHP and will continue to invest in optimizations instead of switching the language they use on their front ends."...... - Nelson Fernandez from Bookmarklet