8.  ashleymadison.com

Originator(s): Darren Morgenstern (as per reports from CBS news and Yahoo), Noel Biderman (as per reports on MSNBC)

Year: 2001

Worth: $ 6,549,230 (estimated, as per statistics on worthofweb.com)

How it took off: Infidelity is bad. Everybody knows it. But after people tie the knot and are still unsatisfied, this site helps them have an affair. “Life is short, Have an affair,” reads the site’s motto. But whether it’s right or wrong, it definitely is profitable--one of the founders of the ‘service’, Noel Biderman, is worth around $100 million, according to an MSNBC report.