According to the information provided by the software on the "most active.gov.au sites" the Australian government has been very active, with the Australian Department of defence appearing at the top of the list. The non-government domains list doesn't provide much clarity, since many of the originating domain addresses resolve to the ISP who hosts them and these numbers will, of course, include private citizens who make changes to the entries. Trawl through the lists though and you will see some interesting corporate names pop up...
Others have covered the commentary about the motivations of these organisations for editing Wikipedia entries, so I'll focus on another perspective.
One of the challenges for organisations trying to access their customers through using Web 2.0 technologies and online communities to reach their customers is working out how to deal with the fact that some online communities may not be what they seem.
The WikiScanner experiment highlights the fact that some participants in these communities may not be who they say they are and may not necessarily be participating for the reasons for which the community was originally established. We need to be pragmatic - the very nature of these communities and tools means that we can't stop this sort of activity, so we need to use good practice to make sure that these activities do not compromise the intent of these intiatives.
Setting up an online community or web 2.0 resource is not something that should be done without a plan. The purpose should be clear - to both the organisation that is doing it and for the people who choose to participate.... and avoid subterfuge - a lot of damage can be done to a brand or reputation if you try to engage in web 2.0 activities under the guise of independence or anonymity. Be open, be honest and wherever your community chooses to step outside the intent and purpose, make sure that you deal with this in a manner which is consistent with the stated purpose of the community.
My message in this isa simple one; don't be fooled by the apparent simplicity of Web 2.0 and online communites. We have been working with these concepts and the technologies that support them for a number of years and there are plenty of tips and techniques for getting more out of them ... and for managing the realities of these new, flexible and open environments. Call in the experts (and don't listen to the first baggy-pants wearing ad agency kidwith a shagy haircut and 7 iPods) and make the most of this exciting technology and the great relationshiop and brand building things it allows us to do.