A bigger opt-in list can mean
bigger list-management headaches...

Suppose you joint venture with someone who drives traffic to your site. Or a colleague recommends your newsletter to his e-mail list. Sounds good, right?

Sure, but you can easily wind up with multiple addresses for the same person. This will also happen when unsuspecting Web surfers respond to your ads -- or subscribe to your lists -- more than once. And it can take you hours to find these duplicates!

If you aggravate the folks on your list -- if you keep mailing them several copies of your messages -- you're dead in the water.