Should a criminal get their hands on one of these email addresses, and combine it with leaked name and AFF registration details, they would be able to mastermind a convincing phishing attack or, with a little more research, instigate a blackmail campaign.
Channel 4 TV quotes a former user of Adult Friend Finder (AFF), Shaun Harper, who said he visited the site but quickly decided it wasn't for him.
Company officials could not immediately be reached for comment.
But in an interview with Krebs On Security, Avid Life Chief Executive Noel Biderman was cited as saying the company suspected someone who had had access to internal networks as being behind the breach.
For those of you harboring secrets behind a website paywall, a word of warning: your skeletons are now easy targets for cyber criminals and nefarious 3rd parties around the globe.