From Google Custom Search Blog;
This saves time when you want to make a quick change to your metadata. If you have data you would like to be displayed on your site, such as reviews snippets, you can submit it directly to Google instead of putting it in publicly visible markup on your pages. For added security, you can even choose to add a private key to your Pagemap and we will only serve it in Custom Search results when that key is provided.Enjoy the Pagemaps and richer snippets Sphere: Related Content
We hope you enjoy the added convenience these new submission options offer. Let us know what you think in our discussion forum.