About 7 years ago, flying a Beech Baron 58, I noticed in the descent the manifold pressure gradually increasing despite reducing the throttles the usual 1" man. press. per 1000ft. Brought the throttle/power lever back all the way to see, and found that it was no longer connected to the linkage, and that the engine had gone to full throttle as the linkage was spring loaded that way. I turned around and returned to Lusaka and landed using the mixture to roughly control power until touchdown when I pulled the mixture to ICO.
A couple of years later, two friends returning to Lusaka in a Cessna 206 had exactly the same problem, however, in this case the engine went to idle as an AD had been issued requiring removal of the spring so that the engine would not go to full power. Fortunately for the pair, they managed to land the aircraft on a busy main road (the only flat space around) and miss everything except a telephone cable which snapped, with no damage to themselves or the many onlookers.
Apparently, an a/c in the US had gone to full power after the linkage broke and crashed because the pilot was unable to land the aircraft in this state, although I can't guarantee the truth of this event. This prompted the AD.
Having had first hand experience of this particular problem, I know which way I personally would like the linkage to go in the case of a breakage. I can't see the "safety" in having an otherwise perfect engine going to idle. We don't all fly over flat, uninhabited farmland!!