You guys posting that traditional relational databases can handle the load of internet scale applications kill me. You mock this guy who has a legit problem that everyone
who has ever run an internet scale
technology is very familiar with.
NoSQL isn't some passing fad invented by high school kids.
Luckily, most of you will probably never discover that fact for yourselves, because you'll never have experience with a successful internet-scale architecture. Relational DBs are just fine for internal "enterprisey" apps, or for your hobby website that drives an astounding 1200 page views/month, or for your failed attempt at launching a web service that only ever garners 300,000 users, so you can continue to delude yourselves that there just isn't a problem here, and SQL is the only skillset you'll ever need.
For the elite few who actually achieve success, you'll totally know where the OP is coming from. Intimately. And you'll either be very glad that there is a path (hadoop, cassandra, mongodb, etc) to migrate to that solves your problems, or you'll be very glad that you started with one of those solutions in the first place.