Canadian parent company Avid Life Media, which owns the site, has offered a reward of Canadian dollars $500,000 (£240,000) for information about the Ashley Madison hackers.
Mr Biderman, a former sports lawyer, launched the website in 2001. He said at the time that he wanted to offer the same opportunities for both women and men seeking extra-marital encounters.
However some of the journalists and security experts who have trawled through the leaked data say there appear to be many more male profiles than female ones.
The site's name was made up of the two most popular names for baby girls in the US at the time - Ashley and Madison. But surely, encouraging adultery and therefore heartache etc, is not the most honourable of acts.