So, since these users want to receive emails from us, the system proposed simply won't work.
We've spent a fair amount of time refining our process, and still have ways to go, but this is the current process:
1. User is not logged in, wants to get a price alert on their favorite protein. They click the button.
2. A modal popup comes in, only asking for their email.
3. They're now logged in, and the alert is saved (but not activated). They're told to check their email.
4. We send an activation email via Mandrill.
5. They activate, when entails entering a password and their (optional) full name, and all price alerts are now active for them.
6. After they activate, we send them on over to a welcome page, showing them where they can see their settings.
This process is as simple as we can make it. The only thing I want to change is some of the verbage in #4. Right now it's a blanket Confirmation email, but doesn't mention the product they want to follow.
Our userbase is all over the map in terms of gmail, facebook, and twitter. I don't trust any of those. So this is our best thing. See my profile if you want to test it out.