I'm pretty sure aperture is a fixed definition, doesn't matter if it's a compact P&S or medium format, the same numbers will give the same size lens (focal length divided by lens diameter = aperture) http://en.wikipedia.org/wiki/F-number
Compact cameras usually have a flange distance of close to nothing, a 3mm f2 would still be tiny, but with the extreme crop factor of compacts they make it seem like a normal camera.
I just realized that it's probably the form factor of the camera that dictates the size of the sensor on those (the larger the sensor the larger the lenses, and thus the larger the camera would need to be).
"Aperture" is a word that is generally mis-used by the photographic community; people often say "aperture" where a pedantic person would say "f-stop". The aperture for a lens is measured in units of length (e.g. a 200mm f/4 lens has an aperture of 50mm). The "/" in "f/4" is actually a division sign, so instead of saying " an eff four lens" you should say "a lens with a maximum aperture equal to the focal length divided by four". Of course, if you said this, virtually noone would understand what you meant; and language is determined by common usage, much to the chagrin of us pedants
The aperture (here measured in millimeters) is, in general, not equal to the lens diameter. You can think of it in crude terms as the diameter of a pin-hole you would make in a pin-hole camera to gather the same amount of light as the subject lens gathers. However, for telephoto lenses, the maximum aperture (measured in millimeters, not f-stops) will typically be pretty close to the front element diameter. For normal or wide-angle lenses, that is not the case. (If you try to do the math yourself, note that the f-stop and focal length quoted by manufacturers are 'marketing numbers', not the real numbers.)
That said, it is a lot easier to make a "fast" (large aperture relative to focal length ) lens for smaller sensor cameras, e.g. 4/3 or P&S. However, larger format cameras seem to have the edge in terms of the actual aperture (measured in millimeters), and thus light gathering abilities, for a given angle of view. As I said before, this lens is about the equivalent of a f/2.8 FF lens, which is old-hat in the FF world.