Blocking search engines from indexing a site whilst under development is a common thing to do and good practice, but it's easy to forget to remove those blocks when a site goes live, so I've added a new check to SiteSentry - Search Engine Indexability.
SiteSentry will now check a site's HTTP headers for the x-robots-tag and home page for a robots meta tag and ensure that let you know if they are blocking search engines from indexing them.