SMT TAXIING NEAR SMA NOT TIED DOWN MAY HAVE MOVED THE ACFT WITH PROP BLAST.

Narrative

I WAS SECOND-IN-COMMAND OF A SCHEDULED FLT INTO AN UNCTLED ARPT. THERE WAS A FLY-IN IN PROGRESS AND WE USED EXTREME CAUTION IN THE TFC PATTERN AND MADE MANY CALLS ON THE UNICOM FREQ. THERE ARE LARGE YELLOW SIGNS ON THE FENCE IN FRONT OF THE TERMINAL WITH ARROWS DELINEATING GA AND AIRLINE PARKING. THERE WERE 3 ACFT PARKED BTWN THE SIGNS; WITH PLENTY OF ROOM FURTHER BACK. 2 OF THESE WERE TIED DOWN. THE SMA WITHIN 4-5 FT OF THE FENCE WAS UNTIED AND UNCHOCKED. WE WERE ABLE TO TAXI INTO OUR PARKING AREA WITH THE OTHER ACFT 30 FT OR MORE BEHIND THE TAIL. WE WERE SCHEDULED FOR A 10 MIN TURN AROUND. AS WE WERE LOADING AND UNLOADING PAX AND BAGS AND WORKING WT AND BAL FORMS; I GLANCED TO SEE IF THE ACFT WAS ATTENDED. I DIDN'T SUGGEST WE DELAY THE FLT; BECAUSE I HAD NO IDEA WHERE THE OWNER WAS AND FIGURED THE BRAKES WERE SET. THE CAPT USED AS LITTLE PWR AS POSSIBLE TO GET ROLLING. AS WE TAXIED OUT WE NOTICED THE SMA HORIZ STABILIZER WAS AGAINST THE FENCE. THE OWNER TOLD OUR GATE AGENTS WE WOULD BE SUED IF THERE WAS ANY DAMAGE. I AM AN SMA OWNER; AND I WOULD AVOID AN AIRLINE PARKING AREA AND AT LEAST TIE THE ACFT DOWN.