It's been worn by both the establishment (Scotland clans, aristocracy, and military forces) and by the anti-establishment (modern-day subcultures), and you can't say that about many fabrics. So what's the theory on plaid's current proliferation? After 9/11, New Yorkers' plaid was spotted through the streets of New York (maybe it was just Fall?), and now the troubled recession times have brought it back.
But, there's another theory. Plaid, along with beards, is a reaction against the metrosexual man of the aughties. Gone is the overgroomed, clean-shaven man, and here is the burly, plaid-wearing dude. I say as long as he doesn't become an urban new-age caveman, he can wear as much plaid as he pleases!
Source: Flickr User bunchofpants