I just looked and there is 1 machine that is part of the domain currently out of 3+ dozen machines on the network (mostly lab machines). The issue has always been that the DC machine winds up just being an old box (or a new desktop PC) and when it would go down it was down for days or weeks so you couldn't really trust it. For awhile it was my old development PC that was 7 years old when it was put in place (not my idea) after the even older machine died that was running as the DC before that.
With 10 employees though I don't know that we really need a DC.