Other sites like math.SE, physics.SE and chemistry.SE already have it. We get enough questions about math that it would come in handy here as well, though probably not as often as on those sites.
For example, here's an answer where I would've liked to use a math formula if possible. I wrote pseudocode instead, which I think is what a lot of people probably do in cases like this.
I guess it could be argued that since we're (mostly) coders here, pseudocode is an appropriate form of expression of formulas. I for one would like to have the option of actual math notation, though.