According to this article from the "Summation" blog, they don't play golf in Silicon Valley, they play The Settlers of Catan!

From Auren Hoffman, writer of the Summation Blog:" In Silicon Valley, golf is mostly dead. It is a game that a few people enjoy and the rest of us have heard of but probably haven't played. The Settlers of Catan (or "Settlers," as it's often called) is booming and is quickly becoming the activity of choice for entrepreneurs here in the Valley. I got into Settlers because Reid Hoffman, the founder of LinkedIn, had been telling me about what a great game it is for over a year. Then one day, some of the engineers at Rapleaf (most of whom had been playing Settlers since college) challenged me to play with them, and I've been hooked ever since."

Read the rest of his blog post here:

In Silicon Valley, Setters is the New Golf by Auren Hoffman