The saying "Do not drink the Kool-Aid" now commonly refers to the Jonestown tragedy, meaning "Do not trust any group you find to be a little on the kooky side," or "Whatever they tell you, do not believe it too strongly." Fox News commentator Bill O'Reilly is known for using the term in this manner.
Having "drunk the Kool-Aid" also refers to being a strong or fervent believer in a particular philosophy or mission — wholeheartedly or blindly believing in its virtues.
Kind of disheartening that such an infamous expression has Indiana roots. The Indianapolis Star has an interesting 30th anniversary story about Jonestown exploring the memories of a Hoosier couple who lost 20 extended-family members to Jim Jones' madness. The couple recall a lot of details of Jones' change from someone who just seemed to be preaching the truth as he saw it:
In a Peoples Temple bathroom, June discovered a box of chicken livers that looked amazingly like the "cancers" that Jones would pull from the mouths of sick people cured at healing services.
"I kept saying to myself to keep quiet," she recalls. "I didn't want to be a doubting Thomas."
Then there were Jones' incessant morning phone calls to issue what June called his daily "orders." He wanted Gene to do things such as change light bulbs in the church, fix his car or tweak the choir practice to suit his needs. The calls became an irritant to June, who had three kids in diapers at the time. "I got disgusted with him," she said.
Scary stuff. In the overheated world of political rhetoric, this or that group of political adherents is sometimes said to be "drinking the Kool Aid" by blindly following a charismatic leader (Obamamanicas being the latest group). It just takes a peek at the real deal to show how exaggerated such claims are.