I,v been around to clear up the mess after two of these mishaps and i think that the post above has a lot of good things to say ,the only thing that i would take issue with is that i think it is better to land on a hard surface rather than grass as directional control can be maintained to a lower speed with the good wheel brake this slows the aircraft more quickly and surprizingly the hard surface damages the aircraft less than the grass.
Both times i have seen this the gear failed to free fall after a hydrulic power pack faiure because of lack of lubrication in the main trunuon (spelling ?) bearing and once on the jacks and properly lubricated the gear worked without a problem.
In my opinion the problem stems from the fact that to get at the grease niples you have to have a right angle grease gun and a lot of hassel to get it on to the grease niple when laying on your back or you have to jack up the aircraft and half retract the gear to get the grease niple to rotate to a position that a normal grease gun will do the job.
I prefer the second option as when the aircraft is jacked up i do a quick free fall check.
In short i think that the lubrication gets forgoten and the problem is masked by the gear powering down.......untill the power fails.