A maven (also mavin or mayvin) is regarded by cohorts as a trusted expert in a particular field, and who seeks to pass his or her knowledge on to others.
Main Entry: ma•ven
Variant(s): also ma•vin /'mA-v&n/
Etymology: Yiddish meyvn, from Late Hebrew mEbhIn
: one who is experienced or knowledgeable : EXPERT; also : FREAK 4a
Yes, well what about the guy who knows everything about something but can’t be bothered to get off his ass and make a website? I know him.