Altslashdot would be run on a number of independent web servers, which would utilise some syncing protocol in order to serve exact copies. The syncing would likely be cheap, because the number of such servers would be substantially smaller that the number of users.
The possibility of running a server would be open, in a hope, that a relatively large number of these would eventually be created. "Hub" sites might exist, that would redirect to the least--loaded servers.
Beside sharing hosting cost, the architecture would enable the exclusion of a rogue server.