Embedding a bad quality font can also make the page/site more heavy (some high-quality fonts share with bad quality ones this : lots of control points and nodes, which are optimized for the high-quality ones, and just superfluous blunders for the others).
But the main point is cross-browser support.
FontLab's Photofonts (.phf) don't (yet?) work with Bon Echo beta 2.x or even MSIE 7 beta 2, but at least you can use them with both Mac or PC commun browsers.