The problem is that in most cases fonts will not show up unless the user has them installed.
Now there have been some technologies to implement automatic font use by the browser, but as far as I know support is still shakey for some, in fact Firefox implemented just enough of certain font technologies to pass Acid3, not to be usable, since they didn't care to implement that specific font technology (SVG fonts).
(Then Acid3 removed that part of the test.)
Anyways while the CSS3 version of font embedding seems nice and seems to work fine in the latest stable release of Firefox/Safari/Chrome, it's not supported in IE9 (or earlier), and as for mobile browsers those are often lesser than desktops feature-wise, not sure if they support it.
Just my two cents as always.