IIRC, part of the mic's size is due to it being a linear array of microphones. This helps determine where the speaker(human) is and focus on his/her voice. It'd be pretty hard to do that with 1 hidden mic. Sure, there are small mics that could be hidden and would pick up your voice(like in a cellphone car kit), but those have a hard time filtering out noise.

_~= Dearing =~_
"WAY too happy about having #99."