Wordpress doesn't scale that well, I assume the database was just overloaded.

It scales just fine. Some of the world’s largest publications run on it.

You're talking about people on Wordpress VIP vs something that is on JustHost. This likely didn't scale at all. Anyhow, you can scale Wordpress, I do it every day in Azure, but it's not something that does well on the fly. I'm not attacking Wordpress.