As you mention, It would also work well for phones with bad web browsers, or devices who's browsers will become out of date, such as the browser for the Dreamcast.

I suspect there are more people on older browsers than you might suspect- There is a staggering number of people still using browsers which don't natively support simple things like PNG transparency, or Properly nested layers.

Essentially, you could think of it as a last-ditch fallback, which ensures that it displays properly, even the UI experience is no longer ideal.

The nice thing is that you wouldn't need to run it on the client-side.. They could just browse to http://fixthispage.com/news.ycombinator.com and it would give them a version as an imagemap.

opera mini, google's mobile search