Why are co-registered leads bad?

Co-registration poses several problems:

First, your subscribers need to be coming directly to you to request your specific information and messages. With co-registration, that's not happening--someone is added to multiple lists via checkboxes and may or may not have intended to sign up to all of those lists.

You have no firsthand record of the subscribe request; in fact, you're taking the word of the company that makes money by selling you email addresses, that those addresses did indeed want that information at any point.

Co-registration inevitably leads to the subscriber receiving a large amount of mail across the multiple lists they were subscribed to, and as a result, they may start lodging spam complaints to get off those lists. These complaints can negatively impact your email deliverability and sending in the future.

Rather than using co-registration, focus on driving traffic to your own website and generating interest in your product/service and site. That way, when someone visits your site they can sign up to receive information from you (which you deliver to them via your AWeber account).