It is infinitely better than your data just suddenly being deleted before you had a chance to get it. At least you get to decide if retrieving it is worth the cost. Also, you can "pay" for Glacier using time/patience because you can download 1gb/mo for free.

All that said I don't think Glacier is set up to deal with a situation where one party inserts a ton of data owned by many other parties, so this is all very theoretical, but IMO it would be great to have something like this.