very interesting question. In really depends on a country.
In US right now people join army as a last resort to get money or find a job and most recrutes are from low-class citizens ( not politically correct term, but you understand what I mean:))
I think that army can give really great skills and only way to get people skills and "stress management" experience. It is the best way to build a man's character.I did not even mentioned yet "promotion" opportunities.
In past, all members of high society were oblgated to serve in the army.
For example, in Russia Empire all members of nobility ( dvoriane) should serve to their country in armed forces, and it was really a honor to be an officer. I know from my family history, that after the boy was born in our family, he usually "assign" to certain military unit. When he became 18, he should serve there starting from first officer's rank.
Right now former military officers are most prominent politics in countries, where war danger is real, like Israel.
In USA, despite of Bush's talk about the war with terrorism, there are no real military danger and military profession is the last resort for social losers ( unfortunately). In our society personal success is more important than the interest of the country.