I think it's considered unhealthy because it's another layer of complexity you have to deal with, and a many-branched environment without any system-enforced me

I think it's considered unhealthy because it's another layer of complexity you have to deal with, and a many-branched environment without any system-enforced meta-structure can result in huge amounts of confusion when things don't go right. You have to train your team and trust everyone to avoid all human error. Example: "whoops, I just merged a bad branch into the master one, but I just left work for the day and I don't find this out until tomorrow morning, let's hope no one checked it out in the interim or we're boned!" With a centralized VCS (or more specifically a single- or few-branched repo), you just tell people to checkout code, commit their changes, and you're done. There are less places to screw up because you don't have a bunch of branches you have to manage. You are less flexible, but this lack of flexibility only becomes a huge burden in a truly distributed (i.e. open source) environment. It's sort of like arguing static vs. dynamic typing. There are many cases where dynamic typing resulted in very painful errors because some variable along the line didn't follow the "gentleman's agreement" that it should be a list and not a string. Though dynamic typing is more flexible and powerful, sometimes you just succumb to human error because the computer trusts you.