Pros:

a tornado of razorblades: SQL Databases Don’t Scale (Hacker News thread)

Cons:

Code Monkeyism: The dark side of NoSQL (Hacker News thread)

Related:

Archives of the Caml mailing list: Message from Brian Hurt

Chris Williams , Co-Curator of NoSQL East, NoSQL: A Modest Proposal

Carsonified: Should you go Beyond Relational Databases?