A number of sources are reporting that the fantastic Camera+ app has been pulled from the App Store:
tap tap tap posted (and later deleted) instructions on Twitter that allowed users to enable the "volume button as shutter" functionality via a back door workaround. This is most likely what got Camera+ kicked off the App Store; other apps with "hidden features" or "easter eggs" like this have been banished from the App Store before, like a flashlight app that allowed users to stealthily enable internet tethering.
The feature in question could be activated only by opening Safari on the iPhone and entering a custom URL, which then communicated with the Camera+ app. (In case you're curious the URL is: camplus://enablevolumesnap).
Apple is certainly well within the terms of the developer agreement to remove Camera+ for sneaking the feature past its reviewers, and you might say that enforcing that policy helps keep all sorts of insidious apps out of the App Store. However, I think Apple missed an opportunity here. As was well documented on their blog, the developers of Camera+ tried to include "VolumeSnap" as a documented feature of the app. Apple rejected it, citing possible user confusion about the function of the iPhone's volume buttons. That's not unreasonable – I wasn't confused, but I can imagine some iPhone users who might be. You could even argue that making VolumeSnap an option, available through the app's settings, could be confusing.
But what if Apple had chosen a third path, somewhere between rejection and allowing the app with full VolumeSnap functionality. Simply put, what if Apple had allowed the URL-based VolumeSnap activation to remain in the app as a documented, tested feature? Most users wouldn't be confused at all, because the VolumeSnap feature is disabled by default, nor is there any visible way of activating it. The only people affected would be those who are savvy enough to find the activation URL and enter it into Safari. Presumably, these are pretty sophisticated users who would be unlikely to get confused by the VolumeSnap feature. Moreover, if they're sophisticated enough to turn the feature on, it's a good bet they could figure out how to turn it off as well.