Why Connecting your YouTube and Google Accounts Matters

Over the last several months many of you who created a YouTube account before May 2009 may have seen prompters asking you to upgrade to a Google account. We first announced this transition in a blog post last July. In the coming weeks, all YouTube accounts created before May 2009 will need to complete the process of linking to a Google account. A Google account is a single-sign in system for accessing all Google products and services. Any existing email address can be used to create a Google account.

http://youtube-global.blogspot.com/2011/03/why-connecting-your-youtube-and-google.htm