What Parallacks? Missed opportunity? :)
Definition: The parallax animation effect is created by two or more layers of an interface moving at different speeds or in different directions in order to produce an impression of depth.
Contrary to the established definition, this articles oddly focuses on Apple's iPad product page as a potential solution or evolution of parallax which completely misses the point.
Apple uses animations that are triggered at scroll positions; conceptually similar, yes, yet provides no sense of depth or exhibits multiple layers.
Good parallax is similar to any animation, it does not interfere with the UX.
Preach! One of the more masturbatory elements of web design.
Article lost me at the phrase "could care less".
...so about 75% of the way through? that's pretty good.