Some more details on that.
It feels stupid that after one 4.3 GB download, each family computer under the *same* App Store license must perform the exact same download again, from who knows how far on the Internet.
A better approach would be for App Store agent to keep a cache of recent downloads (or even partial downloads) and expose that cache to any other computers on the same network, via Bonjour. Technically, this should be easy.
Authentication would still happen via the actual App Store servers, just as now. Only once the download begins, local caches would be preferred over the actual server seeds on the Internet. This is much akin to torrents, but not quite. It would reduce the server load that Apple is getting by some (maybe 10-15%).
What do you think? I find no down side to Apple doing this, starting in some future version of App Store. Luckily, we only have two Macs at home.