I completely agree, but I think that was my point (and I reply largely because I took umbrage with the "Um, no" while really I think we agree)... design patents are very narrow in scope intentionally, and I'm arguing that software patents should be similarly narrow to specifically avoid the problems with the current patent system about which we're both talking.
I used the shopping cart example because of recent news that such a patent has been awarded, and upon reading the patent it does not appear to be a specific implementation at all; rather a very generic implementation that highly parallels an existing physical concept (a shopping cart). It's not that specific implementations shouldn't be patentable (although I may argue that copyright instead of patents should apply in most cases, when the differences are more aesthetic rather than functional, but thus my comparison to design patents), I'm just trying to find a reasonable testable limit to what should qualify.
As you say, patenting the entire store is not what patents are about. I think patenting shopping carts is simliar (unless they have a "novel" feature). Things that work well in the physical world are quickly gaining internet-based analogues.
You're also right about of inevitability, of course, but I think there's a difference between inevitable, and obvious or novel. Lending digital objects (case in point) is an interesting example. A narrow patent on a particular combination of encryption and centrally controlled tracking and limiting methods on how many times something could be shared probably could be patentable, and makes sense. But in this case, the patent has grown to include practically any conceivable implementation, which seems wrong. The limiting factor I suggested was whether there is a physical analog or not. There IS a physical analog for lending, so no matter how long it takes for the first person to build and market code for that should, IMHO, remain unpatentable. I'm not aware of a physical analog for lending something only a specific number of times, so I'm OK with that (although I'd be glad to be corrected).
Definitely an interesting conversation; I think we agree on the salient points.