Craigslist, a network of online communities featuring free classified advertisements, has experienced controversies and illegal activities by its users during its operations.
- On February 3, 2006, Craigslist was sued by the Chicago Lawyers' Committee for Civil Rights Under Law for allegedly allowing users to post discriminatory housing ads in Chicago that violate the Fair Housing Act. The case, Chicago Lawyers' Committee For Civil Rights Under Law v. Craigslist, was subsequently dismissed because of immunity granted by Section 230 of the Communications Decency Act.
- On September 8, 2006, several sites reported that Craigslist's "Casual Encounters" forums in several cities had been compromised by individuals posting fraudulent ads in order to obtain personal information about people. This information, including email addresses, phone numbers, home addresses, photos, etc., was publicly posted online.
- On September 12, 2007, a woman from Minneapolis, Minnesota pleaded guilty in federal court to running an underage prostitution ring through Craigslist.
- On October 26, 2007, Katherine Olson, a Minneapolis woman, was found murdered in the trunk of her car after she responded through Craigslist to what she thought was a job as a nanny; the ad had actually been placed by "Craigslist Killer" Michael John Anderson. Anderson was convicted of his "Craigslist Killing" in 2009.
- On February 8, 2008, a Michigan woman was charged with using Craigslist to hire a contract killer to murder a romantic rival in Oroville, California.
- On March 22, 2008, Bernard George Lamp, 51 of Troutman, North Carolina was arrested for the murder of Bonnie Lou Irvine, 52, of Cornelius, North Carolina; she had agreed to meet him after she responded to his ad on Craigslist.
- In April 2008, a Minneapolis couple were indicted for using Craigslist to advertise for sexual services, and then picking the pockets of those who responded. Eric Christopher Thorsen, 25, and Amy Ruth Bergquist, 30, then used stolen identification, checks and credit cards to purchase merchandise from online retailers as well as prescription drugs. In addition the couple were responsible for tens of thousands of dollars of bank fraud throughout the Twin Cities area. Thorsen and Bergquist ultimately pleaded guilty to trafficking in stolen documents and aggravated identity theft; Thorsen was sentenced to five years in Federal Prison, Bergquist to three and a half.
- In April 2008, a couple was charged with placing an ad on Craigslist inviting the public to take anything from a man's home in Oregon, leading to the loss of his possessions. The couple had placed this ad to cover up their own burglary of his house.
- On May 27, 2008, in Vancouver, British Columbia, police reported that a Vancouver couple had attempted to sell their week-old baby on the site, but the couple claimed that it was merely a joke. The investigation is ongoing.
- On November 7, 2008, after reaching an accord with over forty of the United States' top prosecutors, Craigslist announced that it would crack down on ads for prostitution by requiring people who post "erotic services" ads to provide a working phone number and pay a fee with a valid credit card.
- On December 7, 2008, Matthew Hicks, 32, was fatally shot after robbing, assaulting and attempting to murder Willie Donaldson, 35, in Arlington, Virginia, whom he had met through his girlfriend, who had met Donaldson via Craigslist; in January, 2009, Donaldson was indicted for the murder, but was subsequently acquitted on Jan 23.
- On March 5, 2009, Cook County, Illinois Sheriff Tom Dart's Department filed a lawsuit against Craigslist, accusing the site of "knowingly promoting and facilitating prostitution" in its "erotic services" advertisement section. The company argued that it could hardly be expected to sift successfully through the vast volume of listings it received every day; nor was it required to by federal law; in fact, federal law protected it from criminal proceedings for failure to do so.
- On March 20, 2009, the ABC radio news reporter George Weber was allegedly murdered by John Katehis in Brooklyn. The two had met via Craigslist; Weber was found bound and stabbed fifty times.
- On April 20, 2009, Richard (last name not mentioned) and his mother were attacked in Tacoma, WA with a hammer after seeing a bogus car ad on Craigslist. This was reported in the national news.
- On April 20, 2009, Boston police arrested twenty-three-year-old Boston University medical student Philip Markoff of Quincy, Massachusetts, on suspicion of the armed robbery and murder of Julissa Brisman, whose massage services were advertised on Craigslist in Boston and Rhode Island, and whose corpse was found on April 14 in a Boston hotel. Markoff is accused of first bludgeoning and then shooting her with a gun. He then was accused of another armed robbery of an escort in another Boston hotel several days earlier and an attempted armed robbery at a Warwick, Rhode Island hotel two days later. He was arrested the following week while driving to a casino with his fiancée. He pleaded not guilty. On August 15, 2010, he committed suicide in his jail cell while awaiting trial.
- Subsequent to the Brisman murder, a widely publicized crime, state attorneys general countrywide plied increased pressure on the site "to shutter what they call the nation's busiest virtual street corner, where prostitution runs rampant." Although Craigslist claims to have reduced inappropriate erotic listings by 95 per cent since its accord with prosecutors in November 2008, the attorneys hold that there are still hundreds of such listings emerging every day, and that the company really ought to do more. South Carolina Atty Gen. Henry McMaster threatened the company with criminal proceedings, but it swiftly employed the same defense that it used against Dart.
- In June 2009, Korena Roberts of Oregon was arrested for allegedly killing 21-year-old Heather Snively—who was eight-months pregnant—and her unborn baby, by cutting open her abdomen. They were reported to have met through an advertisement by Roberts on Craigslist for the sale of baby clothes.
- In June 2009, Joseph Brooks, a 71 year old Oscar Award winning film director and songwriter was arrested on 11 counts of rape, including 9 counts of raping women aged 18 to 30 whom he met through advertisements offering film roles on Craigslist. Brooks won his Academy Award for writing the Debbie Boone song You Light Up My Life in 1977 and also directed the film of the same name.
- In August 2009, members of Pranknet, a virtual community established around harassing people via Skype, were outed on The Smoking Gun for activities that also included posting fraudulent ads on Craigslist and then shouting racist, sexually graphic and obscene tirades at people who called to inquire about their ads. Pranknet members also responded to ads placed by young women selling household goods, feigned interest in making a purchase, and when they learned the woman's address, proclaimed they were on their way over to rape them and murder their children.
- In April 2010, a family of four was terrorized by four people who responded to a Craigslist ad for the sale of a diamond ring. The father, 43-year old Jimmy Sanders, was murdered defending his eldest son after letting a couple into their home to look at the ring who proceeded to take out a gun and let two more accomplices enter the Edgewood, Washington home. Four suspects were taken into police custody.