I could also see this being abused. "Plz hlp!!1 my website stop working don't know why, my teacher need this ASAP". Maybe if you deal with the payment issues up front you could get around this (no one's gonna shell down real money up front unless they have a real problem), but it's something to be figured out.
I like it. Maybe even beyond or in addition something like "Code Concierge" -- for a variety of reasons it might be nice to have an ongoing relationship with individual/team/org for problems, advice, etc, that is not a typical consulting agreement, but is more than ad hoc posts to HN or Stack Exchange.