Originally Posted by Paul Markham

Only one way to test it, get a few people to follow the route, sign up and watch the joins in your stats. going to cost you a couple of $100. Then bring the stats here and ask for an explanation stating facts, figures, emails, login/passes and email confirmations.

Or better still go back to them and offer to sell the info. They would probably buy it to stop the drama. It's like sending a pirate a letter asking for payment. ;)