At my old job as a server, I definitely considered them friends, especially my manager. I have gone to the special olympics with her to cheer on her daughter, I've gone out to eat with her outside of work, etc. I don't work there anymore, but I still stop by when I can to see her because she's just a wonderful and kind woman, kind of like a second mom, really. As for everyone else, a lot of the people I worked with were in college with me anyway, so yeah, I consider them friends, especially my AOPi girls. One of them has been hugely supportive of me in deciding to go through sorority recruitment and she's put up with all of my dumb questions and covered for me the day of the Panhellenic tea and I cannot thank her enough.
As for my other job at GameStop, I consider them friends too. The assistant manager there was already my friend prior to getting hired and was the person that got me through in the first place, haha. And then the other guys I work with are all really cool and I talked to them a lot before I was hired as well, and of course when the store is slow, it's good to have someone with similar interests to talk to.
I've been very fortunate in the places I've worked to have co-workers that I actually feel more like I'm friends with than just someone to put up with at work. Of course, it's easier to go into work as strangers and come out friends because at least then, you know why you're there and you can do what you need to do and still have fun. Having someone come into a workplace as a friend already can be problematic, at least in my experience.