I'm almost certain this is a stupid question but, would it be nice to have IS on some fast Primes. I haven't seen any IS features on fast (1.2 & 1.4 ) primes in the 24, 35, 50, & 85 mm sizes. Maybe the feature would alter the weight or light gathering so it isn't being offered. I haven't seen any, do they exist?

You won't find IS on fast primes because it's simply not required. Same for short, wide zoom lenses. The one exception to this general rule is the EF-S 17-55mm f/2.8 IS USM, which is an excellent lens, probably the best of the EF-S series. But you won't get IS on a prime until you get to the longer focal lengths, such as the EF 100mm f/2.8L Macro IS USM.

Slower and longer lenses have IS because they need it.

They need it for still photos as we are using lenses designed for photos not video. For a proper video camera you could expect all lenses to have IS or rather the camera body to have IS.

No, for a proper video camera with interchangeable lenses you can expect some lenses
to have IS, but certainly not all of them. Most short wide zooms for pro video do not have IS.

To clarify what Chris is saying:

The lenses we are using are designed for still photography. In still photography, there is no need for image stabilization on a fast prime because the aperture can be set in conjunction with a fast shutter speed. In still photography, a fast shutter speed makes handheld shooting much easier.

So, the necessity of IS in still photography really doesn't arise until you begin using long lenses, when the magnification begins to amplify subtle camera movement.

If the DSLR craze continues, and is not merely proven to be a stop gap between old school video cameras and a new breed of large sensor video devices that accept interchangeable lenses, I'm sure we can expect to see a variety of fast zooms with IS. However, until then, we are stuck using lenses that were not designed for motion photography.

Except for the 1/3" chip camcorders, are there any professional cameras with IS? I don't know of any.
More than IS, I'd like to see the L lenses with nice long focus throws, like the Zeiss CP2 cine primes.
Zeiss | Compact Prime CP.2 18mm/T3.6 Cine Lens | 1839-197 | B&H