Module allowing users to only view their own content?

Does anyone know if there are any modules that will allow users to only view content that they have created? I would like something like this to build a site where multiple users create their content on one system, but they are only permissioned to view the content they created. This would mean that things like search and notification are restricted to searching/notifying only their own content as well. I imagine that a system like this would impact many modules, so isn't as straightforward as it may seem.

This seems like a very useful module or set of modules to create for people who want to develop services-based Drupal systems--things like private blogs, task managers, etc. I would gladly pay or contribute to sponsor the creation of a module like this if any developers are interested in building it.