I really don't see that this is a good idea. Icons are by definition graphical, they aren't textual. I can see the draw of having vector icons; but we have other technologies for that.
I know people are probably going to tell me an "SVG sprite" isn't possible, but I still maintain that abusing fonts and text like this is a bad idea, even if it does bag you cool CSS3 animations.
I do agree with you, but have you checked the Unicode tables recently? We already had "black queen" and "snowman", but Unicode 6.0 brought us, among others, "Smiling face with horns", "Cat face with tears of joy", and "Hear-no-evil monkey".
Apparently, the world thinks the distinction between text and icon is not that large. Yes, that is mostly for pragmatic reasons, as SMS only does text, and people want to send this stuff using SMS, but it is there, and we cannot deny that.
Given that, I do not think we cannot object loudly against the use of application-specific iconic characters.
I know people are probably going to tell me an "SVG sprite" isn't possible, but I still maintain that abusing fonts and text like this is a bad idea, even if it does bag you cool CSS3 animations.