The problem depends on the graphic drivers, people :
I have a Toshiba Satellite L500-120 ( german/european ) model with built-in Chiconey 1.3 MP cam.
Nothing webcamwise so far works, no matter if under 10.6.x or 10.5.8.
Because I have a unsupported Ati HD46xx gpu I must use dong's great Framebuffer driver RadeonHD.kext for full resolution on my Laptop ( works fine ) . This driver gives 2D basics, but no QE/CI, in other words no OpenGL/3D.
I fear that this is a factor to consider why some of us can get webcams to work and others not. Many of the built-in Apple applications like Photobooth wont work without OpenGL
( QE/CI ), they use it for the "Quartz composer" effects which a 2D driver simply can not deliver ( or only via software rendering, but that seems to be blocked by the apps ).
So we need to dig a bit deeper into webcam support and how it depends on 3D. I guess in Leopard 10.5.x its a bit easier as in Snow 10.6.x, because Snow has OpenGl now even in everyday apps like preview.app and grab.app ( which I can not use with the RadeonHD.kext - therefore 10.5.8 is better for me ) -
As someone said that Tiger 10.4.x had support for more cams I can think that this is true also. Tiger had no need for QE/CI, it could run on any graphics card. ( I had it running on a imac G3 333Mhz with a crappy 16mb ati card and Tiger ran beautiful on that old mac. That hardware windows-like would not even allow xp in its full glory )
Apple slowly adjusts OSX to be totally 3d aware - started in Tiger as an option, in LEopard a bit more and in Snow it is essential. Ichat in 10.6.x makes also use of same effects that photobooth uses..
This needs to be thought of.