I think it would be a lot more ethical if you presented it openly as such, right from the start. For example, the big button at the bottom of the page could say, "Subscribe to our interview-of-the-week series!"
Andrew has spent a lot of time and energy compiling this reference. I don't think it is unreasonable for him to get an email address in exchange. We all love free content but we frankly are not entitled to it.