Buckmaster noted that Craigslist makes itself available to help in law enforcement investigations, though he said he could not say if they helped the Boston Police Department with its investigation into Markoff.

"It's an opportunity to remind would-be criminals that Craigslist is an unwise venue because they're going to be apprehended if they use Craigslist for a crime," he added. "They leave behind a digital trail or digital fingerprint. They're creating loads of evidence that will be used to find them, identify them and prosecute them."

He said developers at Craigslist are working on additional blocking and filtering technologies to keep inappropriate content off the site.