Famous Tom Kyte has written that they (the Oracle) are using the Oracle database as file server and it's working perfectly fine, even faster that normal filesystem, with full transactionality, no performance loss and with single backup.
Yes, but note, they are the producer of the Oracle DB, and for any other user there are cost issues. Using commercial DB such as Oracle for storage of files is simply cost ineffective.
However, with PostgreSQL for example, you can simply run another DB instance only for blob storage. You have then full transactional support. But transactionality costs DB space. There is the need for database to store multiple blob instances for multiple concurrent transactions. On PostgreSQL it is the most painful, since this database stores the duplicates of blobs made for transaction are stored even if they are not needed anymore, until VACUUM process is done.
With filesystem storage, on the other hand, you must be very carefull when someone modifies the file, because transaction can be rolled back and the copy of the file must be kept until the old version is no longer visible.
In the system where files are only added and deleted, and transactional access to files is not an issue, the filesystem storage will be IMHO the best choice.