GRDDL, Drupal, & Microformats

Hey all,
How many of you know about GRDDL ('griddle')?

If you've seen the acronym around but haven't read the spec, then you are missing out.

In short, it's a W3C recommended way to post links to XSL stylesheets in HTML and XML documents.

Those stylesheets are specifically designed to produce RDF/XML from a target document.

So what, you might say.

Well: these GRDDL transformations can be done for an individual document; or an entire xml namespace / xmdp (microformat) profile.

If a couple of large XML schema providers or microformat xmdp wranglers were to simple add in a few attributes & the relevant transformations, a whole lot of locked up data becomes understandable.

So what does that mean to Drupal?

Picture this:
A user posts an event item via their Drupal blog.
They have an upcoming.org url for it - and that url contains hcalendar microformatted data (with the right profile)
They put it into the 'related link' box, and hit 'retrieve'.

Drupal fetches the link, and turns the microformated event & contact data into RDF - using this wonderful GRDDL stuff I mentioned.

Pop! Into a triplestore it goes, and event / contact can be rendered with the post.
It can then also be looked up for later reference in said triplestore (hurray for SPARQL!)

Now, picture this:
The same user just posted an event. They decide to invite some of their friends.
They can't remember all of the emails for their friends, but I've got a linked in profile or two, and a flickr url, or the contents of a blogroll (xfn, anyone?)
Into the magic text field those links go.
Drupal fetches the urls, discovers vcards, translates into FOAF -> into the triplestore.

Drupal could then present the user with 'send email invites' or render 'these people may attend' information.

There's plenty more scenarios you can think of; I'd bet.
What can be done if all microformatted information was extractable?
How would Drupal use it?

What are the big stumbling blocks with these scenarios?
1) A GRDDL PHP client is too much effort... or was.
2) Unfortunately, some of the bigger sites don't correctly publish microformat profile attributes - which can be overcome by deliberately forcing common microformat transformations (hcalender, hcard, etc)
3) Getting your own triplestore running can be tricky.