Some Facebook users temporarily saw a link to a new feature called “custom user clusters” within the self-serve ad tool last week.

Facebook representatives won’t comment on the feature, and the link is now gone, suggesting there was a bug that accidentally made it visible. Users who clicked the link were taken to a page that returned an message that they did not have permission to see the page’s contents. From the URL structure, it seems like the page might be a terms of service page for the so-called “custom clusters.” There is no other documentation about the feature anywhere on Facebook’s site.

We wonder whether Facebook is building a feature that will allow advertisers to save particular targeting parameters to use in later campaigns. The custom user clusters link shared an icon with the Creative Library and Power Editor, which are both advanced features for making ad creation more efficient. The Creative Library, for instance, includes all the combinations of images, headlines and body text an advertiser has previously used. It makes sense that Facebook might be looking to provide a catalogue of an advertiser’s targeting history as well.

This type of feature would give more power to the self-serve advertiser and potentially give users the impression that they don’t need to work with a third-party with Ads API access. In general, though, the social network seems to be working on making its self-serve ad tool more accessible to less experienced advertisers. There’s the recent redesign of the tool that simplifies some of the language around creating new ads and introduces a more step-by-step flow. Facebook has also begun testing a “promote” button for page owners to create Sponsored Stories directly from the posts on their page. Advertisers who want to test hundreds or thousands of ad variations and targeting parameters, however, find that third-party providers make this simpler than Facebook does and they can better optimize their campaigns as a result.

Thank you to Dan Carter for the tip.