That's a good point, and it brings to light an unspoken assumption underlying my post, which is that the use-case is a web-based, read-heavy OLTP-style system. If you were thinking of things like OLAP and data warehousing, then I'd agree with you absolutely.

However, under my re-qualified assertion :-) for large, complicated commits, the logic would either have to be at the database level for it to be in the same transaction, or a solution using temporary tables could be put together for more convoluted calls.

Neither of these are elegant, I'll grant you, but the two basic approaches - longer transactions over logic closely coupled to the datastore, or staged writes - are what most DBAs on high-end databases end up doing anyway, and would probably be reproduced in some form or another in any ACID system, no? Either way you'd still have a database that scales.