iTunes episode page, or The Last Roundup has mysteriously vanished. Now before you all freak out due to the screenshot (later debunked) that has been floating around for the past week about angry emails to Hasbro in regards to Derpy, it looks like the episode is still completely available on the actual Hubworld website. I would think an all out take down would include their site in the mix. We won't know for sure until something pops up though!
Hopefully it's just a glitch in the system. I personally will lean toward that until something more substantial happens.
Until then, watch it here!
Note: Please refer to this post for updates on the topic.