I think there are some errors in the reference for the ShiftIn() function (http://arduino.cc/en/Reference/ShiftIn).
1. The function isn't listed at all on the reference home page. Shouldn't it be listed in the Advanced I/O section?
2. It's not possible to use the Find in reference function on the shiftIn keyword from the IDE (Arduino 0022 on Linux).
3. The Parameters sections seems to have been ripped straight out of the shiftOut() reference without modification. It speaks about shift out and outputs rather than shift in and inputs.
You also need to update the correction links on all(?) reference pages. The link for corrections, suggestions etc points to the old forum on the articles I've checked so I hope this forum is the right one nowadays.