Failure? The economy stays the way it is right now, you'll see a lot of people taking this route. Let him know that he'd be doing EXACTLY what millions of folks have done since World War II (and before).
Behind his friends? Not if he plays it smart. If he invests in the college fund programs they have he's set for school afterward. Nowdays it would be hard to find a military base that isn't offering several options for college classes on post; at one point they were also available on some ships while deployed, although I don't know about today. They were from major colleges, in some cases, and usually pretty transferable; and they were affordable as well. In a technical field he'll be getting training and EXPERIENCE far in advance of what his peers will be accumulating in the civilian world, and likely will also get experience as an entry level manager and trainer. He'll develop a work ethic that (IMHO) you rarely see in young people his age that haven't been there.
I can't stress enough about talking to all the branches, even the Coast Guard. Remind him that recruiters are salespeople; a few lie, but lots are stingy with certain facts
. He should let them know he's talking to everybody, too.
Now ... if I could just convince that youngest daughter of mine ...