Yahoo is trying to drive down costs and get rid of products and features it doesn't need or which don't make financial sense anymore. The latest on the chopping block is Yahoo Messenger. Messenger itself is safe, but several of its features aren't.
The Yahoo Messenger Pingbox is one of them. The feature enabled users to embed a fully working Yahoo Messenger client on websites, making it possible to get in touch with visitors without them having to run the desktop client.
It also makes it possible for visitors to contact the site without having to install Yahoo Messenger and to do so anonymously. They don't even need a Yahoo ID.
But the feature is on its way out, Yahoo is dropping it, which means that starting December 14, 2012, it's going to stop working. If you don't want a dead script hanging around your site, you're going to have to remove it.
This means deleting the code from your site and, to make sure, removing it from Messenger as well. This can be done by going to Messenger > My Pingbox, in the desktop client, > Manage Pingbox. There you can delete all the Pingboxes you may have.
Yahoo Messenger is also dropping support for Windows Live Messenger interoperability, Live Messenger itself is being killed off by Microsoft. The Public Chat Rooms are being shut down, along with the phone in and phone out VoIP feature.