We're well aware of the issue with the amount of My Little Pony content that has been flooding the site a bit for the past several months. And we're also well aware that simply blacklisting my_little_pony causes problems browsing the site normally. Believe me, we don't like it either.
People seem to think that the simple answer is just "don't allow My Little Pony anymore". And they're right, that would be the simple answer. However, I, and the e621 team, are not lazy admins. We don't want a simple answer that greatly reduces the amount of (perfectly legitimate) content the site receives. We don't want to point the finger at some of our most dedicated uploaders and tell them "You are TOO dedicated to continue posting the content to this site that you want to share, so you may no longer post any of it at all." That is not fair to them, and it's not fair to great number of people that do enjoy seeing so much My Little Pony on e621. Therefore, we need a better answer.
The better answer is in the works, and comes in the form of two major advancements in site functionality: 1) ALL e621 users will be able to make use of the blacklist, even those without accounts, and 2) The way the site handles blacklisted pictures for users is being completely overhauled, so that you will no longer have empty or nearly-empty pages. Every page will be completely full of art, no matter what you've got blacklisted (unless you blacklist everything, I suppose).
All that this issue with My Little Pony has done is underline a critical area of site functionality that needs to be improved. It is nothing but the site failing to provide you with the experience that you were looking for. Therefore, we will make the site better, and currently plan to do so as mentioned above. But the one answer that we will absolutely not implement, as long as I'm e621's lead admin, is to ban specific content simply because we get too much of it. That is the lazy and destructive way out, and that is not how I'm going to run this site.
Updated by Riversyde