Still Learning MySQL, MSSQL, Oracle?

I had long thought that it was stupid to implement data consistency control at application layer when I first started coding with PHP and MySQL. Now, I notice that I wasn't that stupid at all, given that most relational databases are "optimized" and partitioned to allow intensive I/O and higher scalability... As a result relational databases became more like object databases which was introduced in the 80's.

As the web evolves, web applications becoming more and more demanding... Now web giants like Google, Facebook, Ebay and Digg are starting to drop relational databases and going back for non-relational storage solutions for better cloud computing. They called it as NoSQL.