with d2r coming up and other games and the size of some guilds i think it would be useful for leaders and approved members to be able to do this
useful for things like
wenseday 8 pm est we running chaos 8 hours
or
as a pm-everyone please sign up for xxx event or post availability for xxx

could be a useful tool with guilds to help communicate with limited abuse potential because you can leave the guild or remove ability to do so from someone abusing the feature
only available to guild leaders by default