Google made an announcement of ending support for all legacy Blogger accounts and blogs after June 25th, 2011.
After, Google acquired Blogger in 2006, all new accounts were created using the official Google accounts system, and then begining in 2007, the search company started the process of moving all the legacy users over to the Google accounts system.
Now, four years later, "we're finally at the home stretch of the transition. For a number of technical and operational reasons, we've decided to finally end our support for all legacy accounts and blogs after June 25th, 2011. So if you have a Blogger account and haven't logged in since 2007, you will lose access to the account and associated content permanently unless you update to the Google Account system before June 25th," informs Google.
"Updating to the new account system is easy and should take just a few minutes. We really do value all of the content that has been created on Blogger and we hope that as many people as possible will reclaim their blogs. If you've been avoiding this task for a while, we encourage you to head over to the Legacy migration page and update your account," Google noted.
Google also said that they'll be sending a similar notice later this week via email to all of the email addresses associated with the legacy accounts in their database. And, there after will also make another announcement with more specific updates on the transition.
[Source: Blogger Buzz]