I agree that slide decks suck as a sharing medium (unless you go to the trouble of adding "notes" under each slide, and share that, but then you're better off sharing a different document). Martin Fowler puts it very well in this post: http://martinfowler.com/bliki/Slideument.html
I can see how sharing a slide deck would dilute the value of a talk. At the same time, sharing my slides lets me reach more people. They might learn more by watching the talk, but it's a trade-off.
There's also the question of the legality of sharing these slides on websites such as InfoQ or Parleys, where the slides are synchronized with the video. But I guess option (c) could work for these.
Given how it's a slide deck, this probably isn't a big deal for distribution. But if it's important to you, I'm sure you can OCR the final product, and that wouldn't end up embedding the fonts. Unfortunately that's sort of a roundabout process.
This is surely an annoying process bound to put anyone off of commercial typography... unless you're already typesetting your presentations in Illustrator. Which, admittedly, I haven't been doing. But now that I think about it: I do a lot of stuff in Illustrator, and Illustrator is so. much. better. than Keynote.
I don't understand why I should OCR the final output, though, since I already have access to the "raw" text. If I were to OCR it and generate a new PDF, I'm back to square one, since I'd need to specify a font. Unless you meant that some people might want to OCR my public PDF to access the underlying text, since it only contains images?
In the end, I guess I'll simply use a font with a more permissive licence (free or commercial).