well, the current popularity of military styles in mainstream culture might be linked with a increasing "militarization" of the political and social sphere - i agree with that...
...but when it comes to subcultural dress codes, the meanings of military apparel are of a much more complex nature. in general, subcultures that "borrow" certain clothing styles from other social contexts have the tendency to re-contextualise these items. hip hop for example has a longlasting tradition in this practice, incorporating sportswear (adidas), workwear (timberland boots - formerly associated with backwoods lumberjacks), sailing gear (does anyone remember the helly hansen craze of circa 98?) and even golf wear (ralph lauren, hilfiger) into the repertoire of its fashion. sometimes the reasons for adapting certain styles are obvious (i.e. breakdancers wearing sweat pants and sneakers for practical reasons), sometimes they are only decipherable with some background knowledge about certain cultural traditions (i.e. chinos being a integral part of the west coast latino culture, originally worn as a reference to the outfit of (mostly mexican) agricultural workers in the first half of the 20th century).
military styles in hip hop can mean different things: Public Enemy's black leather style was clearly a reference to the appearance of the Black Panther Party and therefore to a certain political militancy, whereas the Wu-Tang Clan or Mobb Deep are/were dressed in camouflage gear because they consider it to be the appropriate outfit for a "inner-city warzone". and arguably none of these groups wear army clothes in praise of one of the wars fought by the US military in recent years...
(i have to admit the fascination of hip hop artists with all things military has also taken very bizarre turns - like Master P's No Limit soldiers posing with golden artillery cannons or 50 Cent's infamous Gucci labelled bulletproof vest...)