Typekit is a funny concept to me. While I can respect and admire their ability to build a successful company, I think the blog post shows just how rose-tinted are the spectacles worn by these font services:

Second, we could innovate on the business side as well.
We could sell fonts as a service, and use a subscription
model to eliminate Byzantine licensing and usage issues.

I wonder how much money they would have made if they'd sold fonts with a simple, one-term commercial licence fee, just like stock photography, music, icons, etc.

I know there's no way I could ever use their services with any of the clients I've had, because you simply can't factor in an ongoing cost that is unrestricted and controlled by a third party when giving a fixed price quote for most clients. However, I've spent significant amounts of my own and various companies' money to buy good quality fonts for other uses, and would surely have done so for web fonts as well if anyone was willing to take my money on that basis.

Few sites used web fonts when we got started;
today, new sites seldom launch without them.
Typekit now serves nearly three billion fonts
per month on over one million different sites,
including some of the most recognized brands
on the web.

Well, good for them, but since Netcraft reckon there are currently over 400 million Web sites and there are only a handful of font services, that suggests to me that perhaps 1% of the Web is actually using these services.

From the start, our vision has been to make
the web more beautiful, readable, and fast.

Unfortunately, what they've actually done is cause millions of pages to look terrible, indeed sometimes outright illegible, because most of their screen fonts simply aren't as good at body text sizes as the tried and tested Georgia, Verdana, etc. And there is no way that downloading a font from a third party service, even one with a great CDN, is faster than using a native one that's already installed locally.

Herein lies the fundamental problem with the whole web-font-as-service concept: at body sizes, there is rarely enough difference at typical screen resolutions to justify a change from the old favourites (and such changes are usually ill-advised anyway), while for one-off uses like headings and pull quotes where distinctive fonts can make a worthwhile impact, the web design community was managing just fine already.

As higher resolution screens become the norm, perhaps this will change, just as tiny pixel-drawn icons are giving way to scalable vector-based artwork (but it really shows on smaller or lower-resolution screens where you do still want a 16x16 or 32x32 icon and the vectors haven't been carefully crafted to fit pixel-perfect at that kind of scale). Even then, it's hard to see how you can justify paying a substantial amount of cash every month to use fonts on web sites, when no other on-line stock resources work that way and fonts for other uses don't work that way either.

Still, I wish them well, if only for the benefit of those users who can fit in with their business model and do find it worthwhile. I don't share the pessimism of some here about the Adobe takeover, because one of the few things Adobe has pretty much always done well both technically and in terms of management/legal stuff is fonts.