[acoliver]

First off, if you're writing granny's addressbook it doesn't matter what you use. RDBMS, NoSQL, filesystem, it will work, who cares. I assume that this is at scale. It is a perspective of bill rates I guess :-) Not many grannies hire me to write addressbook apps :-)

Secondly, prototyping your straight JQuery/HTML to MongoDB or Couchbase 2.0 is SIMPLER than to the RDBMS where you must do XML transform first.

Search in RDBMS with ORs and LIKEs is hard and not a good idea for the RDBMS or your middle tier or your user (reduced capabilities with more complexity).

Storing images in the DB vs say a clustered FS makes everything from replication to performance to scalability. Get a few TB of BLOBs and tell me this is a good idea.