It seems they're hosting this on Google Pages – i'm not sure why, maybe it was easier to set up. But obviously Google hasn't waived the bandwidth limit for the gmaps.examplesgmail.com account.

The blog post now works, but going directly to the page (http://gmaps.examples.googlepages.com/gpolyletters.htm) or trying to permalink to the map still gives the bandwidth exceeded message

[Fixed autolinking. -Philipp]

Correction,
the page is http://gmaps.examples.googlepages.com/gpolyletters.htm

I added a) to the end, and refreshing the pages sometimes allows it to load, other times the error is displayed

Right, the problem was not the geocoder limit but the Google Pages limit.
We used it because of its simple hosting features, but we'll moving samples to Google code project hosting from now on (revision history! open source! :).

FYI, if the error was that we had exceeded the geocoding limit, the likely result would simply be that it would fail to find any address. But you'd still be able to write on the map. :)
Anyway, I enjoy this blog alot, keep it up. :)

Thanks, I updated the post with a correction!

Maybe they're having bandwidth issues from people trying to find Supplemental Pages in the search results. It appears right now that Google is not parsing and indexing Supplemental Pages and that about 80% of the formerly visible Web content is now Supplemental and unavailable to non-site queries.