Dig it, I don't want to be "that guy"that pulls the fire alarm just because some kid is smoking in the boys room, but I think this could be a serious safety issue that we should all be aware of. The next time you are doing a "walk around"on your post 1973 bike, take a look at the rear axle nut. If the axle has more than one (1) thread showing you should be suspicious about whether your axle is properly tightened or not.
As we have seen, if the left hand chain tension adjuster has bottomed out on the shoulder of the axle, all sorts of bad things can happen. These include, but are not limited to, high speed wobble, sudden shifting of the rear wheel alignment, sticking brakes, sudden lock-up of the rear wheel, general loss of joy-joy feelings, cats sleeping with dogs (okay, that was over the top) but you get the idea.
Of course there are always manufacture tolerances that blow this out of the water, but lets error on the side of safety and spread the word to be on the look-out for this.
I hope that some of the more experienced members will chime in on how to diagnose this problem without all of us running around with our hair on fire and having to tear down the rear end just to verify that the problem doesn't exist.