However, propaganda - either political or corporate - does not always bear an official stamp. Propaganda operatives will sometimes work for years in the shadows, anonymously originating spam email chains, starting a blog under a pseudonym (!), secretly sponsoring newspaper columns, paying off television news producers to air specific stories that reinforce their concepts, planting the seeds of ideas in the media, even in movies and works of art. Propaganda takes time to sink in, and repetitive exposure over extended periods of time is the key. It can take the obvious form of a billboard ad on the side of a busy road, or it can take the subtle form of a scary news story in the local newspaper.
The truth is, propaganda does not necessarily consist of lies, and need not contain factual errors. It's all in the choice of what is presented to the viewer or the reader; picking ideas that support your goals, and omitting opposing ideas. By carefully selecting the viewpoints presented to the audience, one can influence the audience's perceptions.
An anti-gun group may pay journalists to focus on emotionally-charged gun crime news stories (i.e. "Local Teenager shoots cat with father's BB gun.") instead of focusing on a foreign genocide against unarmed civilians (i.e. "915 Tutsis Found Decapitated in mass grave"). A pro-gun group may pay a film maker to show the hero using a firearm to defend his family against a chainsaw-wielding maniac. A church group may start an email chain about how Stalin was an atheist, and an oil company may pay people to go to blue-collar dive bars and rant against Greenpeace over a few brewskis.
The art of propaganda does not consist of shoving a fabricated lie down someone's throat, but rather to use deceitful psychology to progressively bring someone to believe the lie of his own accord over an extended period of time.
P.S. Oh and never believe anything you read either.