From a conversation with a "developer":
"What do you think is the most important aspect of a database?" I ask.
"Performance!" The developer says.
"What is performance?" I said.
"Well it should be fast!"
"Fast at what?"
"What kind of queries?"
"All kinds, everything must be really fast."
"What about reliability?"
"What about it?"
"Well, shouldn't you be able to trust your database to save the data you tell it to save verbatim?"
"No, we do that in the application, the database just has to store the data, really quickly."
"Doesn't the application need time to make sure the data is valid?"
"Of course, but the database is much slower at that."
"Ok... so how do you do these validations?"
"We run queries on the database to see if the data we are about to send actually exists before we send it."