I've substantially changed my example, so it now fetches country data using Ajax.
The biggest problem with using Ajax is that the Arc web server doesn't support .js files, which is a big oversight for a web-targeted language. Consider this a bug report suggesting support for .js static files. (Really the design should allow arbitrary static files with arbitrary mime-types, rather than hard-coding the list.)
If anyone has Arc running on a public web server and wants to run the Ajax example, let me know and I'll add a link to your site from my page. (My hosting isn't suitable for running Arc.)
Actually, the Anarki supports exactly what you want with static files: a root directory for static files, and a table mapping extensions to mime types for them.
And there's a typo on your page: you don't close the code tag around "/getcontents?field=population&name=value", so the rest of the page is in monospaced font.
That said, your site is consistently fantastic, and I find it amazingly useful. Please keep it up!