The code that generates list-structured pages spits out a page of n items, then saves a closure that will keep going if asked. Since closures can't conveniently be written to disk, you have to gc them after a while or you'll have a memory leak.

It may be overkill to use this approach if you just want to generate the frontpage, but the advantage is that it's very general. You're not limited to displaying a range of items stored in a list somewhere; you could be displaying things you're computing on the fly.