Apple rejects iPhone camera app for using volume controls for taking photos
taptaptap.com
taptaptap.com
Whether or not Apple should review/approve apps is a different question. However, given the current system, it looks like the system worked as well as one would want any review/approval system to work.
The situations are also pretty drastically different: Pastebot is using music-playing to get background operations to work, which will capture clipboard content passively, not via the volume buttons. Meanwhile, Camera+ is trying to use the volume buttons actively to perform a function which is not volume related. Prediction time: if they attempt this, it won't get past the review stage, or will be shot down shortly after.
That's a silly thing to say: obviously some people might profit with an incorrectly managed App Store. For example, many people profit handsomely in very badly managed countries.