Let's say you're just getting started using ikiwiki as your blog, switching from something else and converting the data over from it, as more and more people seem to be. Which is great, but you don't want to flood your aggregator.
You probably set up the blog with a line like this on a page named "blog" of your wiki:
[[inline pages="blog/*" show=30]]
Problem is all the links and guids and other less than stellar things that rss agregators use to prevent dups and flooding have changed and now all 30 pages are going to flood aggregators. As of version 1.16, ikiwiki has a nice new feature that can help deal with this:
[[inline pages="blog/* and created_after(blog)" show=30]]
Now only pages created after the blog page itself will show up on it, while all the old ones will still be available as archives.
If you flooded your aggregator before this, I suppose you're forgiven. Though it was even possible to avoid flooding before this feature, with some difficulty. :-)