I don't see differing thoughts, just differing conversations:
Harman Kochar implied a per-advertiser opt-in ( via the co-registration ). I support that idea too.
Edward Gildea talked about creating products out of non-PII data ( personally identifiable information ) -- which isn't what you're talking about.
Ken Carpenter seems to be talking around the issues ( but I generally agree with what he says ).
Just to clarify my point:
- I think Co-Branded marketing can be dangerous if done improperly. It can be very effective and have great open rates + is a great premium sales item ( like what Ken said ). The problem is that every email out from you has an unsubscribe button -- for your core list. If you have multiple campaigns, you need a lot of internal overhead to ensure you're not overloading these people with messaging ( ie, 1 marketing email per 7 days, max)
- You have 2 ways to "opt-in" someone.
Type A - Implicit Opt-In. This is what your question seems to ask for approval on. You amend the Terms of Service to allow you to share data with Partners. Someone clicks the "ok" button when they register, or misses a TOS change and is converted over, then forgets about it. Whenever they click an ad, you automatically share their info without confirming with them.
Type B - Explicit Opt-In. If someone clicks on the ad and signs up for your site or promotion, they can select/deselect a checkbox to explicitly share that data back to the partner. That explicit opt-in is valid for that advertiser and that advertiser only.
I'm against Type A, and every PR backlash I've seen has been on that model.
Type B is the industry standard for co-branded promotions ( publishers , major brands, etc )
Also , with the "TypeB" Explicit Opt-In , you generally don't amend your own TOS/PrivacyPolicy; instead you add a quick clause /disclaimer onto the registration form that supercedes your TOS. it's usually something quick that states "after registration, the information exists in 2 places , and they're opting into the other company's TOS too".
Last note on the co-branded stuff -- if you're passing the partner the email addresses, you generally want to have the checkbox pre-selected. It increases your list size , and you're not sending the messages so Conversion Rates and OptOuts aren't your problem. If users get annoyed, the partner's "new" mailing list suffers. If you're sending the emails yourself, you generally want to have the checkbox unselected -- because the emails are coming from you , they'll be linked to your opt-out pages. if users get annoyed, your core mailing list suffers.