The original tweet that ignited the furor read: "Going to Africa. Hope I don't get AIDS. Just kidding. I'm white!"
Sacco, then the communications director for the Internet company InterActive Corp (IAC), owner of such popular websites as Match.com, Dictionary.com, OkCupid and Vimeo, posted the remark as she boarded a long flight to South Africa.
Sacco had less than 200 followers, US media reported, but the message was soon forwarded to a staffer at the website BuzzFeed, who re-tweeted it and ensured the message was widely seen.
"Justine Sacco should get fired..." and "Total LOSER!" were some of the milder reactions posted on Twitter, following Sacco's tweet.
Several Justine Sacco Twitter parody accounts quickly surfaced, featuring mashed-up photos, including one of Sacco being stomped on by riot police.
Sacco was unable to respond for hours, as she was on the plane with no access to the Internet.
In the interim, #JustineSacco and #HasJustineLandedYet began trending on Twitter, especially in the United States, Europe and South Africa.
Upon landing in South Africa, Sacco deleted the message and her Twitter account with no comment.
But on Sunday, she issued a statement, sending it to South African newspaper The Star and US broadcaster ABCNews, apologizing.
"Words cannot express how sorry I am, and how necessary it is for me to apologize to the people of South Africa, who I have offended due to a needless and careless tweet," she wrote.
"For being insensitive to (the AIDS) crisis -- which does not discriminate by race, gender or sexual orientation, but which terrifies us all uniformly -- and to the millions of people living with the virus, I am ashamed.
"This is my father's country, and I was born here. I cherish my ties to South Africa and my frequent visits, but I am in anguish knowing that my remarks have caused pain to so many people here; my family, friends and fellow South Africans. I am very sorry for the pain I caused," she said.
After the controversy erupted, Sacco's employer issued a statement announcing that they had "parted ways" with her.
Sacco's "offensive comment does not reflect the views and values of IAC," the company said, adding it takes "this issue very seriously."
IAC added a word of defense for its former employee, saying it hopes "time and action, and the forgiving human spirit, will not result in the wholesale condemnation of an individual who we have otherwise known to be a decent person at core."
Not everyone joined in the kick-her-when-she's-down response.
"What happen to Justine Sacco last night could only be enjoyed by those diseased by their own self-righteousness," read one Twitter message.
"Sticks and stones may break bones, but words on Twitter will always hurt you," read another cautionary tweet.
The moral of the story, as several Twitter writers noted, was to think about what you've written before posting it.
[Image via AFP]
