Many people answer a question like this: "How good is postgres at storing big blobs, relative to small things?" Postgres is indeed worse at storing large things. However, I think the most interesting question is something along these lines: "What's best, storing everything in Postgres and accepting that inefficiency for the big blobs, or implementing transactions, replication and/or backup with a part of the data in Postgres and the big blobs elsewhere?"

I'm awfully fond of having working backups, and postgres' performance problems with the blobs haven't been big enough that I've really noticed.