Lake Zurich, IL
"How Fast is Too Fast to Be Practical?" What the hell is that supposed to mean? The whole point of bandwidth is (and has always been) enough.
Enough for everyone on a LAN to have a good experience, or
Enough not to have to wait a too long for that ISO to download, or
Enough to fill up your hard drive with porn each month. Ad infinitum...
Too fast? Ridiculous premise. Fast enough should be the goal. For the vast majority (who don't visit DSLR) cable or DSL's regular tier is fast enough. As demand changes, they'll have to adapt or die.