The camera module in pygame can read from /dev/videoN but only from the default input number 0, with the default norm.
Some video capture devices (like this one) must be given an input number and norm in order to work properly.
For example, to read input 1 as NTSC (not PAL) on that Kworld USB2800D device, you do this in mplayer:
mplayer tv:// -tv device=/dev/video1:input=1:norm=NTSC
In pygame there is no way to specify the equivalent of "input=1:norm=NTSC".
The neccesary details are specified here(linuxtv.org).
[Thanks to 'nrp' for explaining this to me on IRC.]