As a WMF presenter, I'd like to respond briefly.  First: the WMF has an internal budget as well, and its decisions about who goes/does not go to Wikimania have their own troubles/nuances/benefits, etc.

In my own opinion, the WMF is employed to do development work for the community.  I feel that tipping the balance too much toward either WMF or community presentations do both a disservice.  If Wikimania were to be only community presentations, surely the complaint would arise that WMF was absent, does not know about all the good work the community is doing, isn't adequately supporting them with its work, etc, and conversely WMF employees would feel the community is left ignorant of the tools they are building on the communities' behalf.  And obviously if Wikimania were only WMF presentations those employed to serve the community would be doing all our time talking when we should be listening!  A balance is needed (and we can have a great debate on what the right balance should be; I didn't hear any complaints from participants about the balance at Esino Lario, for example).

Wikimania is a great opportunity for communication between different facets of our movement, both planned and unplanned.  My own experience from leading problem-solving teams in various capacities is that the unplanned interactions are actually the most important.  Generally, if you *know already* that X is working on Y which is of interest to you, then you can with more-or-less difficulty find X to exchange ideas about Y.  But how do you find people when you have no idea who they are or that they are working on something of interest!  That's the opportunity you get by gathering all sorts of different Wikimedians in one place, and having them eat and socialize together.

As such, my personal opinion is that purely "merit-based" participant selection --- both of community members and internally at WMF (usually based on having an accepted presentation) --- runs the danger of not including enough folks who are there (a) to listen, not talk, (b) who would be inspired by things they did not expect and could not have predicted on an application.

If I were to make this a concrete suggestion, I'd suggest including some number of "perfectly fair" random scholarships/participant selections, so that even non-presenting WMF employees and first-time community representatives get a chance to listen to each other, learn unexpected things, and be inspired.

  --scott

ps. Having a "report back" expectation also seems fine and useful.