"As you may be aware, we have been releasing new versions of Yahoo! Messenger for iPhone quite regularly to give our users quality experience on the iPhone. It is our hope that users will upgrade to the latest versions as time goes by.Continue reading : We’re retiring Yahoo! Messenger version 1.0 for iPhone on June 15th, 2010
In an effort to maintain our high quality and security standards, we will officially retire the Yahoo! Messenger version 1.0 for iPhone and iPod Touch on June 15th, 2010. This means that if you are currently using this version on your iPhone or iPod Touch, then you will no longer be able to sign in and use it after the retirement date of June 15th, 2010..."
Posted @ Yahoo! Messenger Blog