Can colleagues make close buddies?

Well, I've been wondering whether colleagues can make good buddies? I mean can you hit off a very good comfort level with colleagues? I have been fortunate to make some very good friends while I was working at Hewlett Packard. Not one, I've made four good buddies from HP. But in general, it is hard to make good friends while in office. We come across people from different backgrounds and different mindset at office. It is hard to find someone with the same wavelength as that of you. Most people I see keep to office more at a business level. Also, given the volatile nature of the our industry where a person stays with a company for not more than 4yrs (like me :-) ), it is hard to understand and to open up yourself to people within the small time span. I wonder if this thought of mine is same with most people or is it something only I've encountered or observed?