Removing the ability to send links in direct messages is the first time Twitter has truly crippled its service for me.
UPDATE: Per TechCrunch, this appears to be temporary, caused by a technical choice to try to address an upsurge in spam, not a permanent change. Here’s hoping. I’ve updated the headline of this post.
Twitter posted this message on its DM help article:
We’re restructuring back-end elements of our direct message system. As a result, users may be unable to send some URLs in direct messages. We apologize for the inconvenience.