Did a web search and found an incident on this web site:
http://www.ndcap.us/dept/safety_alert.htm
"While taxiing out to fly an AFROTC Cadet Orientation flight, the pilot taxied across a parking row instead of following the taxiway. He accelerated while crossing over a tiedown rope and it was picked up by the prop. Before the engine could be stopped, the tiedown rope had damaged the prop, spinner, bulkhead and the lower cowl.
Normally, a pilot can taxi into a parking spot over a tiedown rope without the prop picking it up. This is because the aircraft is close to idle power and slowing down. To increase power and accelerate through a tiedown area is just asking for trouble. There are numerous hazards in a parking area - chocks, grounding wires, ropes, tiedown cables, people and other aircraft. It may take a little longer to taxi on the taxiway, but you can feel confident that you'll encounter fewer hazards."
(A bunch of other prop strike incidents on that web page that show some things to be wary of.)
The tie-downs used for the airplanes at the field I fly out of are metal chains with S hooks on the ends. While anything is possible, I'm not too worried about one of those getting picked up by a prop.
