Former FBI agent and ABC News law enforcement expert Brad Garrett said Craigslist is a first choice for many looking for sexual services.
"By some sources, it's one of the leading avenues to promote prostitution because it's so easy," he said. "You place an ad, you say, 'Come to Hotel X, at a time and date' and a service is provided. It's really an ideal environment for criminals."
Earlier this year, New York radio anchor George Weber was murdered in his Brooklyn apartment, and police said they believe the killer answered Weber's Craigslist advertisement offering $60 for "rough sex." Weber was stabbed more than 50 times.
Gay Talese, an author who writes on the sex trade, whose most popular book, "Thy Neighbor's Wife" came out long before sites like Craigslist existed, said such sites are making the problem much bigger because the players are anonymous.
"It's instant communication, it's instant sex, it's sometimes instantaneously a tragic situation," Talese said. "The reason it's definitely bigger is because any sense of caution or guilt associated with sexual interchange of a commercial nature is eliminated now."
Just last November, Craigslist entered into an agreement with 40 state attorneys general to eliminate some of the anonymity by requiring credit cards to post these erotic ads.
The company CEO told ABC News they are deeply saddened by the events and are "evaluating the incident to see if they can better protect Craigslist users."
But experts say little can be done to prevent criminals from using the Internet to stalk their prey.
After the arrest today, Craigslist CEO Jim Buckmaster issued a statement, saying, "We are very pleased to hear that the person alleged to have committed these crimes has been arrested, and we will continue to provide law enforcement agencies with any assistance necessary to prosecution of the case."