Facebook has added a feature so that you can ask friends whether or not they are in a relationship. It sounds like a way to help the somewhat creepy, but as always advertising is likely the key.

The new feature applies to any field in a user’s profile that they’ve not yet completed, such as phone number, relationship status, educational background or workplace. If you are a Facebook friend with that person, you’ll no longer see a blank in that slot, but rather an “Ask” button. For now, the button will only appear for US users.

If you click the button, you’ll have to fill in a box explaining to the person why you want the information. The person then chooses whether or not to add the information. They can also choose whether only you can see it, or if they want it made available to a wider group such as Facebook friends or anyone viewing their profile. If the person chooses to reject the request, you won’t get any notification.

At first glance the feature seems very weird. It only works for people who are Facebook friends, so you’d think most friends would already have most of the information the person has chosen not to list, unless there’s a good reason why you should not be aware of it.

The feature probably makes more sense for the type of users who don’t restrict themselves to “real world” friends on Facebook and instead add people they either don’t know or only know in an online context. And if you think it’s appropriate to use a Facebook button to ask for somebody’s relationship status (rather than just send them a message or ask them in person), well, that’s your lookout.

In reality, trying to figure out the benefit for Facebook users with the new feature is missing the point. Any time a user responds one of these requests, whether they give the information to the inquiring friend only or make it public, they are also giving the details to Facebook. More details means more focused advertising, and that’s the ultimate goal of the site.