[wvenable]

You're putting a lot of faith into this. The fact is that performance, scalability, features, and correctness are a trade-off. RDBMS is optimized for certain conditions and these NoSQL databases are optimized for other conditions. NoSQL databases are horrible at things that RDBMS's do extremely well and vice-versa. NoSQL isn't some magic discovery -- of course they're going to run into problems that RDBMS solved years ago!

Your argument for small boxes seems to be the same argument for one large box. My (extremely average) desktop has a terabyte of storage in it -- why do I need a bunch of boxes running a distributed database? One big server is a hell of a lot easier to manage than a fleet (a fleet!) of small boxes.