I'd say that the simplest explanation for the .22 shortage is that it's the only round that people who shoot can find/afford right now.
Sure, it's overpriced, but at least you can still shoot!
Now we're in a position where too many people had the same idea, and now .22 supply is dwindling too.
Two of my three LGS's had .22 last time I checked, but it was very expensive (~10 cents/round) and they only had the cheaper brands such as Winchester Wildcat.
I bought 100 rounds for my new rifle, but didn't go as far as to pay $50 for a brick.
Another problem here in NY is the looming new laws for ammo sales.
I'm hoping to buy as much as possible before that happens, as I wish to avoid the inevitable teething problems that they will have when this poorly thought out law is first implemented.