It could be that Leadbolt sold user information just like FB and other well know organisations also do. In my mind, all users information are available for a price.
We may signup to various websites and they say they will not share user information but further down the road they will have a change of heart when they realise the information they are sitting on is a gold mine. They will make 100% profit from doing so because they already have the information at no extra cost.
In this cash strapped economy where everyone is looking for yield there will be more to come.
@marcusxman you're right as it is no telling how these people obtained this information as I have not used this account for years. All I know is that no one's information is safe anymore.