Every time I have redesigned a website or intranet over the last 12 years I have asked the question of what is the minimum monitor resolution we need to support for customers.
I was very glad when we could stop catering for 640x480 resolution and make the new minimum 800x600.
Since then each time I check I have still found a dedicated minority of users (down to around 2-3% now) still on 800x600 resolution monitors.
Over the past three years I've seen a number of major sites move to 1024x768 as the minimum resolution (including most news media sites) - for a large commercial entity it may make sense to abandon the few remaining 800x600 users to focus on their more lucrative audiences.
With today's computers starting with a default resolution of 1024x768, the users still on 800x600 are most likely to be older, have poor vision or a vintage computer. They may be using internet access in public areas or simply not have the knowledge or confidence to change their monitor resolution.
These are the people most likely to draw on government services, so my conclusion is that government agencies cannot leave these people behind.
However if government has a commitment to serving all citizens it must also ensure that the other 90%+ of people are well catered for. Presenting a fixed 800x600 site, or even an expanding site which simply increases the whitespace at higher resolutions doesn't provide additional value for the majority of users.
It could be considered reverse discrimination - limiting citizens who own modern computers and have good eyesight to basic 800x600 pixels worth of information at a time.
So my view is that while government agencies must support 800x600, they must also seriously consider adaptive designs through the use of css (Cascading Style Sheets) - a standard HTML tool - to present better designed and more effective websites for the majority of citizens.