i always wondered about this myself. i think the answer lies in how the DM for your campaign will interpret it.
this offers more questions however.
does an unconscious character still get will saves? will they automatically fail their save if you cast "charm person" on them?
personally, i would go with unconscious = willing. i think part of will saves is making a conscious effort to resist. that being the case, if you are unconscious, i would say that a "charm person" would automatically work.
however i can also find it very plausible that will saves are more of a persons "innate" resistance, similar to how your heart still beats, even if you are unconsious.
but then, i'm not a DM, and i'm looking at this from a player's point of view, and would love knocking out bad guys, making them lose their will save. but, as is usually pointed out, you have to think that the bad guys could do the exact same thing to you.
however, would you rule unconscious = sleeping?
if that is the case, it may be good to catch an NPC sleeping, but what if a PC is caught sleeping? imagine going to sleep and waking up dominated.
