Dive Summary:

• Optimal, Inc. CEO Robert Leathern writes at Huffington Post that no serious marketing should go into 2013 without know how to use Facebook's "Custom Audiences" feature, which allows users to target existing customers by performing a match with hashed versions of opt-in email addresses.
• Using the matching system, marketers can push specific, more appropriate ads to customers in places where another ad would have already appeared.
• Leathern writes that the system can display mobile newsfeed ads in less than an hour.

From the article:

"... As most marketers know, emailing customers or prospects has a high opportunity cost -- a non-relevant email will either get consigned to the spam bin or worse, the user clicks the 'unsubscribe' button. Custom Audiences instead allows marketers to show a more relevant Facebook ad to a customer, in a spot they would have seen another ad anyway. And just as with email, creating multiple sub-segments of the user base allows targeted offer delivery to specific groups instead of a "one size fits all" message. ..."