To someone who knows database internals this may be an easy question, but can someone explain in a clear way why storing large blobs (say 400 MB movies) in the database is supposed to decrease SharePoint performance, i.e. file-upload performance, site browsing, displaying lists, document opening etc.? Remote Blob Storage aka moving files out of the database, leaving only a reference, is supposed to solve this, but what exactly - at the bottom level - is the difference? It's obvious that backups would take longer with giant files stored in the database ... but what operations exactly are impacted and what's the underlying mechanism of it (i.e. in what way are files stored on filesystem outside of the database accessed or stored differently)? It's not like the actual binary content columns are indexed.
I would say that the problem isn't a SharePoint problem (SharePoint is really speaking just a ASP.Net website reading and writing to a SQL database), but more of a SQL Problem.
I found a good article where Microsoft did some research on the topic. Read here: http://research.microsoft.com/pubs/64525/tr-2006-45.pdf