The side of a bus shelter usually displays advertising, not a subtle technological discussion on the state non-relational distributed key/value databases and their comparative value to RDBMs systems.

For example, compare slides 15 (RDBMs):

http://www.slideshare.net/mattetti/couchdb-perform-like-a-pr...

and 52 (CouchDB):

http://www.slideshare.net/mattetti/couchdb-perform-like-a-pr...