Writing blocks to a flat file is not very ACID, and there is no attempt at something analogous to BEGIN TRANSACTION/COMMIT when updating the block chain or indices, so a failure part-way through a reorg is very likely to leave the database in an inconsistent state. Granted, both of these problems are outside of BDB and do not reflect on the strength or weakness of BDB.
I would say that bitcoin is effectively using a NoSQL "style" by not taking advantage of consistency guarantees, or of a relational model, both of which I think it would benefit from.
Well if the BDB transaction fails, there will be no pointers to the extra crap at the end of the flat file and subsequent blocks will be added later, so all that would happen would be a bit of extra space would be wasted (in theory). Not quite ACID but not quite leaving the database in an "inconsistent" state.
Anyway, I think weve overtaken this thread enough...