Using ArcGIS Server to Publish LYR files

I was reading What's Coming in ArcGIS 9.3.1 just now and something that caught my attention was the heading "Better sharing of layers".

For a couple of years I've been thinking that it should one day be possible to author a LYR file in ArcMap, and then to publish it from ArcGIS Server, without having to add the Layer File to an MXD, before it can be published as that larger document. I'm very interested to see if this capability is to be included in 9.3.1, because I can immediately think of one of our key clients using several ESRI products in its GeoStack, who could benefit if this is the case.

I'm also interested to learn how "ArcGIS Online sharing supports ... Organization, community groups, and control access to layers". It seems like ArcGIS Online is heading in the direction of overlap with the Geography Network which is far greater than today.