I think more importantly than not getting fired or finding a job, working with people you actually like makes work seem a lot better. I currently have a job at a small company and the Venn diagram of my interests and others on the dev team may not have any intersection at all. This makes work pretty boring.

Working with friends probably means not only that you can socialize well together but that you are working on something that you all enjoy or at least all bitch about together. That's the real benefit of having friends at work.