Searching for examples of civil servants taking part in other people's sites

So, we've been busy interviewing everyone and anything that won't run away from us.  As usual, asking questions has produced even more questions.  And that's where I'm hoping some of my many (6) readers might come in.  Can you perhaps point us to:

1. Examples of places where civil servants or other public officials successfully engage in other people's user-created sites? (I'm loath to say in other people's discussions, because if they were making useful additions to wikis, that'd be fine too).
2. Examples of public servants who have been stopped from engaging for what seem like either good or bad reasons.
3. Examples, good or bad,  where governments gave either monetary or other support to non-government user-created websites.  What did they give? What did they get out of it?
4. Stand out, clear-as-daylight examples of Uncontroversially Good Things that happened when government officials did deign to contribute to other people's sites. And vice versa.

The feedback from people here and on the UK & Ireland DoWire list and on eMint has already been brilliant and perhaps more useful than they know. Please keep rack  your brains and/your inboxes/Google/your friends' brains to help with these questions - the better answers we get, the more we have the chance to shape the way that Government evolves to react to the user-generated era.