Or your datastore can take care of doing that for you, c.f. BigTable. This is one of my main gripes with most of the current set of NoSQL offerings — they leave too many decisions in the hands of developers.
Whilst it would definitely be advantageous for all developers to understand the intricacies of various CPU and OS scheduling algorithms, it's not an issue that most developers have to deal with directly. The App Engine datastore, in particular, proves that it is possible to create NoSQL datastores which don't force developers to think about issues like load balancing.
Well - in many cases they leave the decisions in the hands of developers because they have made a conscious choice to let the developers decide.
BigTable is more than anything a filesystem - it is NOT a database. It lacks true user configurable indexes, custom sorting, querying etc. These features and the data storage requirements to support them are a very different prospect from what a filesystem (even a distributed one) needs.
Whilst it would definitely be advantageous for all developers to understand the intricacies of various CPU and OS scheduling algorithms, it's not an issue that most developers have to deal with directly. The App Engine datastore, in particular, proves that it is possible to create NoSQL datastores which don't force developers to think about issues like load balancing.