It does (requires?) transaction logging, but

Corruptions still happen. I think a big part of it is the Jet DB engine it is back-ended by... that or maybe good old NTFS.

The trend (starting with 2007 and continued/revamped with 2010) is to use more, smaller DBs with redundant copies (BPOS uses triple redundant) spread across multiple servers. It doesn't really solve the problem, just makes it easier to manage when one goes tits up. Of course, this also results in pretty severe server sprawl. For one client, we'll be putting in 200+ servers for 50k seats. Not really apples to apples here, but we also manage a Zimbra install for 28 million seats with around 1200 servers. Neither Exchange nor Domino really scale very well for big Enterprise environments - too tied to their departmental roots IMHO.