[atwebb]

Depends, you can try and find companies in different business sectors and fill in gaps for each (with permission of course). The company pays with their list (and a fee to you?) which another could use. As long as it doesn't affect their competitive advantage, it could be a freeish way to grow the list. Not every scenario but there could be a niche, especially if you were the middle man and masked where the data was from and where it was going.