It depends if they just joined and say "LOL I CAN HAS HELP WITH UR STUF PLZ Z", and I have no idea who they are, then I usually say no.
However, if it's someone who joined previously, and says "Hey, can I help?" it depends on what I'm doing.
If it's someone I know and like, then always yes.
So "maybe" button.
oh wait, it doesn't exist.