Matt Raible (now a full time employee of LinkedIn) posts about how he came to work there as a result of a consulting project where he helped them evaluate open source web frameworks against a framework that they had built in-house. In the end, he recommended enhancing their internal framework to include some of the best attributes of the open source frameworks, and he was hired to build a team to do just that. Anyway, the post contains a lot of wisdom about making these kinds of technology decisions.