> > Pins that need to be inputs but at some time may be uncommitted,
> > for example when an input device is removed/unplugged, should
> > have a pull-up or pull-down resistor so they don't float
>
> Is this true for analog inputs also?

No, I wouldn't think so. I can't see any specific advice in the manuals
for commiting unused analogue inputs

The main reason for using a p/u or p/d resistor on a digital input is to
put it in a known state, both electrically and logically. It may not be
important what logic level a floating pin could be at any time, but
electrically it's not desirable because of the switching power used,
which may affect the PIC or other components

http://www.piclist.com/techref/logic/xtrapins.htm

Obviously an analogue input is required to accept an indeterminate
voltage, so I doubt if digital design rules apply

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