Co-registration poses several problems:
- Your subscribers need to be coming directly to you to request your specific information from you.
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 leads inevitably receive a large amount of mail across the multiple lists they were subscribed to, and as a result start lodging spam complaints to get off those lists. These complaints can negatively impact your email deliverability.
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!).