Sorry, but I have to disagree. I have made many lasting business relationships that I can rely on that have never spilled over into the realm of friendship. I have business contacts/relationships that have lasted 10+ years where if I ever needed a job, it is only one phone call away. I have never had a single social venture with any of these people in my network. In fact, I have no idea who or what they are outside of work.
I have a wife, kids, and a huge extended family. I also have friends outside of work that I am very happy with. I just do not feel the need to socialize at work. I go in, get my work done, and get out. I build relationships at work based on reliability, productivity, and integrity. These things can often become muddied by personal relationships, especially productivity (at least that is my opinion).