Amazon seems to delay the confirmations on some of their digital purchases; definitely MP3s and maybe video (IIRC). Believe at least in those cases, it's to make the CC processors happy (batching lots of small single purchases). Apple does the same thing for the iTunes/App store, though it seems to be on the scale of days instead of hours there.

edit: to be clear, by "delay the confirmations" I meant to say "delay the actual purchase"; the purchase(s) doesn't actually get charged until their time threshold hits.