When 9/11 happened, the boy I was seeing was a few months shy of 18 and I was afraid then that they'd reinstate the draft. They didn't and I hope they never do. Besides my own selfish reasons of not wanting loved ones sent away, I really think it takes something away from our armed foces.
There is something to be said about all the men and women who are serving because they WANT to. There's something beautiful about it being volunteer [not as in unpaid, but as in not required]. I think if you took a bunch of those people who want to serve and add to them a bunch of people who are only there because Uncle Sam said so, it would hurt morale.