sweet! looks like this thing is quickly taking shape

i'm in IT but i'm not a web developer so i tend to look at things from a more system integration and less coding perspective

so, here's my suggestion. based on Daniel's requirements (e.g. personal blogs), i think it would be best to implement a standard and popular open source solution, such as WordPress MU. see: http://mu.wordpress.org/
my reasoning for this is as follows:
- it's free, open source and it's in PHP. so hard core developer's would easily groove with it

- it would be easier for non-hard core developers (like me) to participate in the creation process. also, design-wise, there are a lot of templates available to start from.
- it has solid developer support, highly customizable, lots of plugins, and scaling will not be an issue, RSS ready, blogging-engine in tact and tested. no need to re-invent the wheel.
assuming we go with WordPress MU, i imagine DhO becoming something like http://scienceblogs.com/ (i.e. dedicated members with blogs in addition to the wiki, and who knows what else

)
my two cents.