I agree with the "travel shock" theory, but my own evidence is anecdotal as well. I don't think I'd really want to waste a bottle to test the theory under controled conditions.
My family was camping last summer, and my parents were to come up and join us. I called my father before he left and asked him to bring a bottle of beaujolais that I had left at his house the day before. So he drives up the mountain roads (about 30 miles from his house) and I see the bottle has been bouncing around on the floorboards the whole time. I let it rest as long as I could (about 2-3 hours) and when I opened it, it was extremely disjointed, and what little sediment there was was still dispersed making it seem chewy, tannic, and rough. Quite a disappointment, and not at all like the other bottles I had consumed.