Tank in wire obstacle trial
 

Apparently non-barbed wire was considered as a tank obstacle early in the war as evidenced by these pictures taken at Ft. Belvoir in 1940. The wire may have stopped this early tank but I doubt it would have been effective against the heavier, more powerful tanks on the horizon. The tank used in these trials was a rarely seen de-gunned T2E2.

Sapper a single piece of wire as short as two meters has been known to stop a modern dozer if picked up and raped around the axle. It cuts out the oil seals with disasterous results.