I'm not sure it's a good idea. Working relations are not of the same nature as friends relations, they are less stable and they are, by default, less important

I'm not sure it's a good idea. Working relations are not of the same nature as friends relations, they are less stable and they are, by default, less important. They are also highly affected by the company policies and by individual careers evolution. Ultimately, your relation with your coworkers is constrained by your individual roles in the company. Believe me, you don't want one of your best friends to become your manager. I'd rather prefer my coworkers to become my friends, than my friends to become my coworkers.