sometimes, you only don't want to talk to everyone on your contact list.
to do this you have to block everyone and then unblock who you want to talk to, which noone likes doing as it takes too long and if said people find out you blocked them they get angry at you
.
these problems could be easily solved by:
being able to set the status you will be at when you next log on
OR
if you could change the status you appear to be at for different contacts... your family group could see you as permanantly busy doing homeowrk and your friends could see you as online and up for a chat!
OR
we could have both, now that would be qool wouldn't it