I serendipitously came across this PPC ad for National Geographic through Google, which automatically inserted my email address into a conversion box for newsletter sign-up:

After some research, I found that Google is beta-testing this features, and has invited a select number of websites to take part. So unfortunately, there’s very little data out yet on how successful this feature is in getting email opt-ins.

On the surface, it looks like a great feature. It allows searchers to opt-in to newsletters easily.

But there may be some problems. One, I assume it only works for those consumers with gmail accounts who are logged in to Google while searching. Two, it may be a better conversion tactic for sites with eCommerce offers (here the ad is advertising National Geographic’s travel expeditions, not the site’s content). After all, it’s easy to get someone to sign up for a brochure of stuff they want, but they’ll probably want to visit your website before agreeing to get your weekly (daily?) content-heavy newsletter.

And three, its unknown how merchant-friendly Google will be with this feature. Can merchants hook the feature to their email service providers — or does Google plan to add email list services to its Google Apps product? And will you be able to use double opt-in features, a definite best practice for creating clean lists?

Is your subscription site one of Google’s Beta-testers? If so, what’s been your experience?