I personally prefer the forum for announcements, you can see when a new topic exists. A minus would be that people don't read the forum that often.
And with personal messages their is a risk that you "delete" them without reading. I sometimes do that when I login and quickly click on something and the message/s dissapears without to know what is in it or who sent it.
Their was some time ago a discussion about mass messaging, but it wasn't implemented.
