All speaking requests in which people go out and represent the Foundation should be under the auspicies and supervision of the Foundation.
Perhaps, but it isn't currently clear when people are representing the Foundation. Personally, as I'm moving to focusing more on Wikia than Wikimedia, how would I know which organisation I'm representing, or whether I'm not representing either, but just attending as someone who knows something about wikis? Most people attending these events will have multiple affiliations, and as far as I can tell, most invitations go directly to the speaker, not via the Foundation (though that could be because there's never been a central point of contact for this sort of thing within the Foundation). Also, people do talk about Wikipedia without having any affiliation - http://blogs.zdnet.com/BTL/?p=2586 is one of a few examples of Mitch Kapor giving a talk about Wikipedia.
As an example of a talk I couldn't attend, I asked the organisers whether they wanted me to find someone else from the Foundation, and they said no because they specifically wanted a British female Board member, so it's likely some of these events do want specific people, or at least specific types of people, regardless of any official affiliation with the Foundation. Other talks I've been invited to have said they asked me not because of Wikimedia, but because of other affiliations I have (ourmedia in one case), or because I was female (perhaps as a result of me being listed on Socialtext's speakers' wiki).
Finally, when people contact the Foundation asking for a speaker, it is safe to assume that they expect an "official representative."
That might be true, but most of the events I've been to, I've been contacted personally. I don't think that necessarily means they weren't expecting an official representative.
What would it mean for a speaker to attend something *not* as an official representative? Perhaps guidelines on what people can do if they are/are not attending in that capacity are needed. It needs to be something more than just not keeping the money since there generally isn't any offered anyway.
Angela.