On the surface, the fact that you can do mash-ups with Yahoo! Maps doesn’t sound like news. Can’t you do that with Google as well?
Justin Everret Church has opened my eyes.
In HTML, you have two ways of repurposing information: either take the raw data and build a new presentation around it (most common), or repurpose the UI from the existing app wholesale (useful for visual things, or for hosting complex interactions, such as Google Maps)
Using Flash, there is a third alternative: use someone else’s UI layer, but visually alter it and extend it.
In a way, it’s like a visual mash-up. Check it out.