Dear google answers, my rather general question is... why do people
disable power management in their networked desktop PCs and leave
their PCs fully powered-on 24/7?

I know that this is a very open question.  A good answer will describe
specific applications that are "broken" if power management is left
enabled.  There are existing methods for waking-up Ethernet-connected
"sleeping PCs" including Magic Packet and even pattern matching to
specific packet types.  Are these methods not adequate?  What would
need to be changed/improved in a desktop PC, its applications, and/or
in the network connectivity to allow power management to be fully
enabled and used at all times?  Again, a good answer will give
specific examples, possibly cite references and/or web sites, and
otherwise provide a "good argument" (for the given answer).

Thanks!

Couldn't you ask this to the people who disable power management?

It could be that they believe that it will prolong the life of their
computers.  This site discusses this a bit.

http://cma.zdnet.com/book/upgraderepair/ch08/ch08.htm#Heading11

Also, perhaps they just like to use electicity...gives them a *power* trip...

Power trip!!! Good one!

I know my logic (I use the settings on my laptop, but not on the desktops).
In general if you set standby/hibernate at 20 minutes idle it you will
have a paper to write that required 20.1 minutes of thought.  I dont
like having to shake the mouse every now and again when I am watching
a movie (most players have probably fixed this, though).  I also like
to hear my hard drives hum.  When you are used to having them on all
the time it is kinda weird when everything is quiet.
I turn the monitor off when I'm not in the room/awake...but thats
about as much power conservation I give my desktop.  I'm afraid my
laptop will melt a hole through the table if i left it all night (it's
a dell...).