Chris McDowall from New Zealand wrote a wonderful piece that encapsulates the whole concept of open data quite nicely:
The Zen of Open Data, by Chris McDowall
Open is better than closed.
Transparent is better than opaque.
Simple is better than complex.
Accessible is better than inaccessible.
Sharing is better than hoarding.
Linked is more useful than isolated.
Fine grained is preferable to aggregated.
(Although there are legitimate privacy and security limitations.)
Optimise for machine readability — they can translate for humans.
Barriers prevent worthwhile things from happening.
“Flawed, but out there” is a million times better than “perfect, but unattainable”.
Opening data up to thousands of eyes makes the data better.
Iterate in response to demand.
There is no one true feed for all eternity — people need to maintain this stuff.