Why can I no longer screen share via Messages/iChat anymore?

[iMore Question]

I can no longer screen share via Messages/iChat anymore

I use iChat/Messages using an AIM account with my family to troubleshoot their Mac problems by screen sharing. From what I can tell (via blogs and help forums), this feature no longer works, at all, anywhere, for anyone no matter what OS X version they use or iChat/Messages version they use. The icon for screen sharing is greyed-out and has ceased to be supported by Apple. Can anyone tell me if this is a known issue that is being fixed by Apple?