We created EepURL as a trackable shortening service for MailChimp's built-in Twitter integration. At the time, we opened it up to the public, because we felt there weren't enough monkey-based URL shorteners out there.
This service is no longer available for public use. We made this change in order to protect the reputation of the domain and high deliverability rates for MailChimp customers who use EepURLs in their campaigns.
Existing URLs are still being redirected, and EepURL still works in the app.
We're trying to prevent the URL from getting blacklisted.
If you're looking to build your own url shortener, take a moment to look at Shaun Inman's Lessn. Building your own url shortener is a good way to avoid having your links connected to a blacklisted domain name.