Wiki Comparing Discussion Forums and Email

Wiki for comparing discussion forums with email communications
Benefits and weaknesses, or just characteristics.

Add columns for chat and wiki ?

Discussion Forums	Email Communications	Chat	Wikis
public (to participants ... or even to global audience)	confidential (?)
requires login and a few extra clicks	quick
complete view of the discussion
free for subscription or de-subscription	-(felt as spam if not interesting)
provides neat evolution record
Some where between chat and email in terms of formality	More formal at times, can be like writing memos	Very informal, like making side comments or small talk
Well considered, even calculated messages		Spontaneous, reactive, superficial messages