In order to speed up Slashdot and not use up as much processing power, they are batching up the comments, and spitting out static pages every few seconds.
Normally, the page is dynamically created when a person views it.
The reason I say this is because twice I've posted to an article, reloaded the page the article was on, cleared my cache and reloaded again, and I didn't see my post. After a few seconds, it miracuously appeared.
Its a clever idea, it definately will speed up the site, but it will also create more redundant posts, because people don't see what they want to say (because its batched up for the next static page), so they post it. I guess its a money vs redundant content thing...