Just in case you are using Ruby for whatever purpose (esp. in web applications) you might want to be aware of the recently discovered security holes. They can lead to Denial of Service Attacks or execution of arbitrary code. And this cannot happen just under some strange circumstances but might affect applications in general as describe in the Matasano blog.
For more information and updates please check this page and update as soon as updates are available.
Is this the reason for Twitter downtimes? ;-)