TypeKit has a lot of countermeasures to ensure that the fonts are used according to the license, and not by anyone who isn't allowed to or through proxy's or something. I don't know the details but had a run-in with this in the past, resolved soon by customer support. I'm guessing Adobe didn't care for creating a second serving system to serve up these fonts, or the licenses are still restrictive that it requires some added logic.

This is similar to how TypeKit serve their fonts. They wrote a blog post explaining their reasoning: http://blog.typekit.com/2011/08/11/better-web-font-loading-w...

That post claims that fonts don't have a fallback mechanism for when a font fails to load, but fonts have had fallbacks for as long as we've had CSS:

    font-family: "Obscure Font", "Common Font", sans-serif;

I don't know the current state of things, but a failed font download used to result in blank/transparent text in some browsers, ignoring the fallback font.

From the linked page:

"The fonts are served by Typekit, so you can be sure of high performance and stability."

I abandoned Google fonts because of the annoying latency / flash on refresh. The Adobe fonts are smooth on my dev machine. That might be worth the difference under the hood.