I think it's up to the institution, but generally, a BA is awarded for more academic subjects, while a BS is used for subjects that are for a specific profession. YMMV, of course.
Those aren't the only two options either - personally I have a Bachelor of Aerospace Engineering.
That's how I've always understood it as well. Throughout my years in school I'd always have friends and family members question me as to why I was getting a BS rather than a BA since "graphic design is, you know, art".
I've had two interviews so far since graduation. One said thanks but no thanks and wanted someone with more experiences, and the other place hasn't given me an answer one way or another. I've been applying like mad to just about every job that seems like it would be a good fit. What is maddening is that a lot of places want a graphic designer AND a web designer all in one. Our curriculum covered user interfaces and things like that, but never went over any HTML or CSS. That's what the Web Design & Interactive Media degree program is for. I guess a lot of places now want to save money by hiring one "jack of all trades" instead of specific specialists.