It turns your lat/long into a single alphanumeric string. The cool thing here is that as you lose characters from the right side, the sequence remains valid at a lower accuracy, describing a larger and larger bounding box. I could see this being really useful for a site that had location urls matching some collection of data. it’s human-editable enough that people could expand the search area just by editing the url.
Aside from that just being cool, I have a soft spot for services that not only tolerate, but actually encourage URL hacking! del.icio.us is probably the canonical example -- they put it right in front of you -- but Adam Darowski points out1 some other folks that have nicely sliceable URLs, too. And docreader lets you do it along multiple axes at once, causing people's heads to explode.
Hackable URLs appeal to me because they have the potential of making it faster and easier to find stuff and link to stuff. Hackable URLs appeal to me because it's fun to tinker. But hackable URLs appeal to me most of all because they imply trust and respect for users (as opposed to URLs that imply "don't tinker or we'll sue you").
It's also interesting to think about how URL was never supposed to be an exposed part of browser UI, considering how well entrenched it is now.2
- Darowski didn't coin the "URL as UI" phrase he uses. Jakob Nielsen has been writing about it since roughly the beginning of recorded history.
- Not necessarily everywhere, though. In Japan, we saw a lot of ads that showed search terms (or phone-scannable 2D bar codes which encoded URLs!) much more prominently than they showed domain names. Our patient teachers told us that it was because a typical domain name is hard to chunk if you're not a native reader of the English alphabet. And, indeed, when we visited Roy and Electra's Japanese teacher, I noticed that she didn't have the URL field showing by default in her browser. (From what I can tell, the idea of domain names that contain non-ASCII characters is still largely just an idea.)