Flight over densely populated areas

I have been planning to build my own airplane for quite a while, but I have
a nagging question that I never see addressed. FAR Part 91.319 (c) appears
to prohibit flight of experimental aircraft over "densely populated areas"
(whatever that means).

The entire text is: "Unless otherwise authorized by the Administrator in
special operating limitations, no person may operate an aircraft that has an
experimental certificate over a densely populated area or in a congested
airway. The Administrator may issue special operating limitations for
particular aircraft to permit takeoffs and landings to be conducted over a
densely populated area or in a congested airway, in accordance with terms
and conditions specified in the authorization in the interest of safety in
air commerce."

How do the rest of you deal with this? Does the "Unless otherwise
authorized ..." part help somehow? Do you avoid densely populated areas?

Thanks
John