Blogger, owned by Google, runs checks to find spam blogs at Blogger. Obviously something went wrong since they posted this in Spam Fridays:

While we wish that every post on this blog could be about cool features or other Blogger news, sometimes we have to step in and admit a mistake.

On Saturday they posted this in 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.

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.

They also state that:

At Blogger, we strongly believe that you own and should control your posts and other data. We understand that you trust us to store and serve your blog, and incidents like this one are a betrayal of that trust.

Blogger has deleted blogs suspected to be spam before, including their own offical Google blog which was mistakenly deleted, but this is the first time they admit a mistake. And the statement about bloggers owning and controling their posts sounds good. There is always risks using blogging platforms run by others and not self hosted.