That's true. Also, the cable company can segment the "coax" part of the "hybrid fiber/coax" network into smaller sections to further increase bandwidth.
In any event, the issues I've had with my cablemodem have nothing to do with bandwidth and everything to do with poor outside plant maintenance by Comcast. Verizon has the same problem howerver, observe how often you see pedestals with all the wires hanging out and the cover is nowhere to be found.... I never used to see that.
Incidentally, the statement you made, 'While it is true that cable modems may share the same cable that doesn't mean you are sharing the same bandwidth as a "regular network card."'
is an example of the difference between a "broadband" network (using the "technical" definition here, not the "mass-media/consumer" definition of "any high speed connection") and a "baseband" network.
A CATV network is broadband. It is divided into channels. More than one device can be transmitting on the network at the same time, on different channels.
A 100baseT network is baseband. It is NOT divided into channels. Only one device can transmit on the network at a time. Incidentally, this is where the "BASE" in 10BaseT and 100BaseT come from. Baseband.
If you go way back to the late 80s/early 90s IBM used to have two different kinds of network products intended for the education market. One they called "Broadband" and it used a cable TV infrastructure to network computers. Sort of an early cablemodem. I don't know that much about it other than that. There was also a 10Broad36 Ethernet standard which is outlined here:
http://en.wikipedia.org/wiki/10BROAD36 --I'm not sure if this is exactly the same as the IBM "Broadband" networking product, but it is the same idea. Neither of these ever really caught on due to the expense.
IBM also had a "baseband" networking product that used standard twisted pair daisy-chained from machine to machine. I believe it ran at 1mbps and I last saw it in use at Osbourn Park High School about 12 years ago. It was a proprietary IBM network not compatible with anything else. It was their "cheaper" alternative to Token-Ring. In 1995 however regular ISA 16-bit 10-meg ethernet cards were down to $50 each and 10 times as fast so by then IBM's "baseband" was a solution looking for a problem.
Speaking of Token-Ring, I last saw that in use a couple years ago at Potomac Mills Mall in a store. It was connected to (surprise) an IBM cash register.