Yahoo! Freeing Up Unused IDs That Are Inactive For A Year
Here's the crux of it: "We’re freeing up IDs, that have been inactive for at least 12 months, by resetting them and giving them a fresh start. In mid July, anyone can have a shot at scoring the Yahoo! ID they want. In mid August, users who staked a claim on certain IDs can come to Yahoo! to discover which one they got."
If you want to ensure your ID remains yours, just log in with that ID (to any Yahoo! product) by July 15th. Or, today, while you're thinking about it. The ID landgrab returns!