Great cross browser support for "@font-face" and the rise of online font delivery services like Typekit, fonts.com and Google web fonts has completely transformed the landscape of typography on the web.
You can't use that, it's not a web safe font!
Years ago, this would have been hurled across agency offices and on phone calls to clients frequently. There used to be a limited assortment of fonts that you could use on the web without having to worry about if all your users were going to be able to see the same thing. With the introduction of these now common practice techniques and services, you can literally use any font your heart desires (licence permitting).
As with everything, with this new found typographic freedom, there comes a new responsibility not to abuse these new powers.
I wrote this for the Engage Interactive blog so if you're still interested carry on reading after the jump: How many fonts, is too many fonts?