Punk is a subculture that was originally begun with the objective of being anti-establishment, but is now actually the mainstream trend, thus rendering the very principle of punk null and void. What it takes to be a 'real' punk is unknown because every punk thinks every other punk is a poser.
Punk is often associated with anarchy, leading stores like Hot Topic to slap the anarchy symbol on everything possible, when, in fact, anarchy is the opposition to things like government and capitialism, etc., so to be a real anarchist, one would have to not buy things at the fucking mall, thus making 98% of punks under 18 total dumbasses.
Punk as a fashion style has been ground into the ground so hard I never want to see a studded belt ever again and as a musical form, punk has been cut up and incorporated into so many other styles, it's hard to find a 100% punk band anymore. But none of the following are punk bands or artists: Simple Plan, Good Charlotte, Ashlee Simpson, Avril Lavigne, or any band ever called emo ever.
"Omg, this Ramones tee I'm buying at the Buckle in the lower of my local mall next to the Gap is, like, so punk!"