You could leave out the excerpt and it would still be a river. The important thing is that the excerpt be of determinate length, and short enough so you can see a lot of items on screen at the same time.
The main idea aren't the details, but the way its used. I can scroll back to the point where I hit something I seen. Quickly. My memory is perfectly capable of telling me I've seen something before. You can rely on it, people can do this.