Well this thread turned out bigger (and much more productive) than I expected!
To my mind, Wikimania continuing to happen every year is a minor miracle, and one that's only possible with the hard work and dedication of lots of people.
However, it's a miracle that isn't without its problems. The most obvious problem to my mind is that there is a very mixed quality of actual conference programme, and without clear objectives (or at least not consistent objectives). The Wikimedia Conference, by contrast, has a much clearer alignment of the programme with a set of goals, and work happens to follow up before and after the conference.
The second problem is that the responsibilities for governance and management of the conference are really very unclear. We have the Wikimania Committee, we have the local team (and in some cases a local chapter who may or may not be working closely with the bid team), we have the Programme Committee and we have the WMF. (Actually we have the WMF at least twice, as the priorities of the WMF team involved in organising the conference don't always seem to align with those of the rest of the organisation).
In my view, the most useful thing for all these groups to do is to work out who is actually responsible for what, and document it, in public.