C182 PLT HAD AN NMAC WITH A PA60; WHEN THE PA60 PLT DID NOT COMMUNICATE OR LISTEN ON UNICOM. THE PA60 PLT STARTED TKOF ON RWY 19 AFTER C182 PLT WAS ALREADY ON TKOF ROLL ON RWY 1.

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EVENT OCCURRED UNDER LIGHT AND VARIABLE WINDS. THE WINDSOCK LAY PERFECTLY LIMP AND AWOS RPTING A XWIND AT 4 KTS. FOLLOWING MY BROADCASTING ON THE LCL UNICOM FREQ (122.7) THAT I WAS TAKING THE ACTIVE RWY 1 AND DEPARTING TO THE N; I ENTERED THE RWY AND PROCEEDED WITH A NORMAL TKOF. JUST AFTER LIFTING OFF; I NOTED AN ACFT ON TKOF ROLL ON THE SAME RWY; BUT OPPOSITE DIRECTION (IE; RWY 19). (LATER THIS ACFT WAS IDENTED AS AEROSTAR BY RADIO CONTACT.) IMMEDIATELY BEGAN EVASIVE ACTION BY A R TURN; CONTINUING TO CLB. THE AEROSTAR CONTINUED A STRAIGHT AHEAD TKOF. I HAD BEEN MONITORING THE UNICOM FREQ AND HEARD THE XMISSION OF THE PREVIOUS ACFT TAKING OFF (ON RWY 19); BUT HEARD NO XMISSION FROM THE AEROSTAR. THE PRIMARY CONTRIBUTING FACTOR TO THIS EVENT IS THAT THE TERRAIN AT JWN IS SUCH THAT ACFT IN THE RUN-UP AND INITIAL SECTIONS OF BOTH RWYS (01-19) CANNOT SEE ONE ANOTHER. UNDER CONDITIONS OF LIGHT AND VARIABLE WINDS; PLUS LIGHT TFC; THERE CAN BE AMBIGUITY ABOUT THE RWY IN USE; LEAVING IT TO THE PLTS TO COMMUNICATE ON UNICOM. IN THE EVENT OF A MALFUNCTION OF XMISSION OR TWO SIMULTANEOUS XMISSIONS BY THE ACFT ABOUT TO TAKE OFF; ONE IS RELYING ON SEE AND BE SEEN. THIS CAN ONLY APPLY WHEN ONE SEES THE FULL RWY; WHICH IS NOT POSSIBLE ON THE GND AT JWN.