I'll certainly agree with the issues of tool misuse and safety.

Won't agree that experience has much to do with safety - it's about knowledge and diligence. Experience often works against, as folks tend to become lax. "Hey, never had a problem before." Case in point: NASA. Closer to home: advocating ripping operations with a table saw without use of fingerboards or kickback pawls. Rob's specific example of experienced woodworkers sans digits makes the point fairly well.

History works against his point a bit. B&D sold an attachment to fit a saw to a Workmate until a few years ago. Had its own blade guard and bump switch. A dodgy fence and unflat surface did it in. A current manufacturer has resurrected the same idea. Here, the saw is a drop-in mount, so the saw's guard (and a gaping throat) is there. Flimsy piece of crap, and wickedly dangerous. But it has a blade-guard and a bump switch, so the CPSC is happy. Commercial manufacture or not does not designate safety.

My back couldn't take much of Tom's exact method and there are certain other drawbacks such as materials waste, but long-length ripping with a circular saw is a legitimate tool use. Lee Valley and others sell straight-edge tools with saw travelers specifically for the purpose, and there is a reason that thin-kerf rip blades are manufactured in 7 1/2" sizes. There are ways that the waste could be minimized - join up the waste planks to form a usable-width board, for example.

There is a place for shop-built jigs and guides. They need care and diligence in both construction and operation, but can be used to increased safety and desired use.

Honestly, a table saw of any sort is an inherently unsafe tool that cannot be made more than marginally safe. Certain manufactured accessories (such as dado blades) are accidents in waiting. Only an understanding of the risks and diligence offer any amount of safety. I personally won't be making a table saw from a plank - I can't see reasonably working out an accurate, stable buildup that would be as safe as I'd prefer. However, there are other possibilities.

Another item in manufacture (wish I could find a link) is a miter gauge for circular saws. Holds the saw in a traveller right side up, and can also be used in a rip configuration. Not perfect for a repeating rip, but it does offer an idea. Build a 'bridge' to hold the saw over the work - imagine the fence holding up one side, just for an image. The blade would be completely protected, and kickback protection could be easily incorporated. Accurate, stable adjustment of the fence/blade relationship is the biggest design challenge.

If it comes down to rental, resale, or borrowing, a radial-arm saw is likely to be considered. There's often a near-religious fervor in the debate between table and radial-arm saws, but there are certain advantages. Anyone care to chime in on that question?

Thanks to all for the thoughts thus far. Rob, one of your secondary suggestions (high-school shop class) has the wheels turning. Worked out right, could probably get free labor in the deal. Perhaps need a little extra materials, but that's a fair trade. Kid down the street's about the right age...