Having trouble stalking your Facebook friends efficiently? Help is on the way! Facebook is currently testing a new feature (dubbed the "Stalker Button" by Mashable) that makes online stalking easier than ever. So what does it do?

The new feature, which was discovered by AllFacebook.com, appears as a link reading "Subscribe to [Your Friend]" underneath your friends' profile pictures:

Facebook's New 'Stalk This Friend' Button, Currently in Beta

Essentially, "subscribing" to someone means that their Facebook activity will appear in your "notifications" drop-down, like so:

Facebook's New 'Stalk This Friend' Button, Currently in Beta

Unlike the current "Subscribe via SMS" feature, "Subscribe to X" would update you on activity beyond status updates—including whenever your "subscription" posts photos, videos, links, and notes. According to Facebook:

This feature is being tested with a small percent of users. It lets people subscribe to friends and pages to receive notifications whenever the person they've subscribed to updates their status or posts new content (photos, videos, links, or notes).

A few questions remain unanswered: Will the subscription notices only cover posting "new content," or will subscribers be notified when their "subscriptions" join groups, RSVP to events, or "like" things? Will the feature be automatically enabled on all users' accounts? And most importantly: Will users be able to opt out?

The thing is, the information is already public, and we're sure the feature will be convenient for someone (your mom, maybe, or your ex-girlfriend, or the guy who is always trying to look down your shirt at work). But where the News Feed took your activity and put it on a big scrolling list for everyone to see, this allows people to target you specifically, and be notified of your activity automatically. Surely, that's not the work of a company dedicated to privacy and user controls.

As All Facebook notes, this is most likely yet another attempt at adding some Twitter-like functionality to the Facebook, which has an oddly jealous relationship with the much smaller Twitter. But ultimately it seems more like an attempt at making Facebook an even more convenient tool for stalkers than it already is.

[All Facebook via Mashable; pics via All Facebook]