I have always been impressed with the appoach to sharing spatial data in the State of Victoria in Australia.  In 2008 I heard a presentation by Jose Diacono and Danny
Broadbent who were associated with the Victorian Spatial Council.

The Victorian Spatial Council developed a framework for sharing
based on licenses and metadata, not only within the Government of
Victoria, but also among utilities, telecommunications firms, National
Government, other government, quasi-government, and non-government
organizations.  The program is based on the Victorian Spatial Information Strategy, and incorporates the concept of custodianship. 
They have encouraged organizations with data to share to participate in
the program as data custodians.  This is a voluntary program, not
mandated by legislation.

In August 2012 the Victorian Government released the DataVic Access Policy, which enables the sharing of Government data at no, or minimal, cost to users. In 2012 and 2013, raw Government data from all agencies will be progressively supplied in a machine-readable format.  The DataVic Access Policy provides direction on the release, licensing
and management of Victorian Government data so that it can be used and
reused by the community and businesses.

Recently the Victorian Government released its first set of raw spatial data online including data about electoral and planning boundaries, transport
networks in the state, parks and conservation areas, and oil and gas
fields.  The data is available on the government’s Open Data portal. Currently there are about 525 spatial datasets from the Department of Environment and Primary Industries, Department of Justice, and others.  The objective is 1000 datasets on the open data portal by September 2013.