Here you can see some experiments with 'unavailable' shutter speeds and aperture values on the Canon Powershot S5IS.

You might notice that the EXIF data does not reflect the claimed Tv and Av, that is because the camera does not really know about them. The official limits are:
1/1600, F/2.7 near
1/3200, F/8.0 near
1/1600, F/3.5 far
1/2500, F/8.0 far
Values beyond these limits are recorded given that they are not faster than 1/3200 or smaller than F/8. Values outside these extremes are not properly recorded by the camera and are instead shown as 1/3200 and F/8, respectively. Images with exposure within those ranges have been included to prove that there actually is a difference.
The full images can be obtained by clicking the thumbnails.