Document-oriented datastores (aka NoSql) are very popular these days:
There's no reason you can't employ a document-oriented scheme in a relational database. You might not get all the same benefits compared to something like Mongo, but you won't have the drawbacks, either.
For a long time, if you wanted to use document-oriented storage, your only choice was shoving structured data (like XML) into a big column. The relational databases have been adding features like indexing and matching to support that.
Contrast that with Mongo, where they only thing in the database is documents. But that's another topic.
EDIT: the core idea of document-oriented is: you pull the data out, manipulate it, and shove it back in whole. Sometimes, like when you're transmitting the document to the client, you just want to send the whole thing as a blob and let them deal with it. The benefit (and drawback) is flexibility. Validation and correctness of the document is done outside the database.
EDIT EDIT: Another contrast. Imagine saving JPG images, or Word docs in a database column.