The only reason to stuff the stuff into the database, as far as I can see, is that InterMedia can index it for searching.
In the case of webmail it sort of makes sense with java inside of oracle, as the mail message needs to be pulled inside the db to parse the message anyway. Of course they could probably write the encoded message back to the filesystem faster than stuffing it into a table in oracle, but not having access to an oracle set-up, I have no way of telling. The main problem that I have with webmail is that it stuffs the mime-encoded message into the db and then pulls it right back out and sends it. After the message is sent, it is deleted from the db, so I can't really any benifit to putting it into the db in the first place. Even with acs classic, I suspect that doing it that way is actually slower than using the filesystem - especially for messages with large attachemts.
I guess we can't really go about implementing a binary file storage module until we see the shape of acs 4.0 - can we?