“We all like the comfort of the crowd,” says Mark Brownlow in a post at the Email Marketing Reports blog. “The knowledge that others went here before us tells us we’re on the right path.” Because of this tendency to trust the wisdom of crowds, he argues, you can encourage opt-ins to your email list by demonstrating how popular you are. Some suggestions:

Highlight testimonials. If a subscriber sends unsolicited praise, ask if she’ll allow the use of her name and comment; if she will, display the comment at your sign-up page.

Use indicative text. While Brownlow notes he has yet to do A/B testing on the following tantalizing line, he has noticed an increase in sign-ups since its addition: “Over 3,000 marketers, agencies and businesses already benefit from their email subscription…join them:”

Add dynamic social proof-indicators. Icons that display real-time subscriber numbers; widgets that proclaim the number of recent subscriptions; scrolling displays that update whenever someone new signs up: all might play an influential role in someone’s decision to join.

Brownlow does offer a few caveats. If you’ve positioned yourself as an exclusive club with limited membership, or haven’t yet reached the point where subscribers join on a regular basis, this approach might not work. “[Y]ou might actually discourage opt-ins when your widget says you have 23 subscribers and the last one signed up in 2007,” he says. And remember: test every new addition.

It’s OK to crow a little. By adding testimonials or positive stats to your sign-up page, you could boost your opt-in rates.

Source: Email Marketing Reports.