Blogger Buzz: You Are Not Spam: "You knew that already, and now we do too. We have now restored all accounts that were mistakenly marked as spam yesterday. (See: Spam Fridays)
We want to offer our sincerest apologies to affected bloggers and their readers. We’ve tracked down the problem to a bug in our data processing code that locked blogs even when our algorithms concluded they were not spam. We are adding additional monitoring and process checks to ensure that bugs of this magnitude are caught before they can affect your data."