Early last month, Apple announced that their Messages Beta for Lion would be discontinued. The Messages Beta was released shortly after Lion appeared on the App Store last year and offered a way for Mac users to get in on iMessages. Mac users could send messages to owners of iOS devices, as well as to other Mac users.
The Messages Beta was likely a way for Apple to widely test its infrastructure. Less than a year later, Mountain Lion was released and included Messages from the start. Messages replaced iChat, and has since garnered a lot of criticism for its confusing interface and lack of chronological ordering of texts.
Regardless, the Messages Beta will be expiring this Friday. After that date, don’t expect it to work – it isn’t surprising, given Mountain Lion’s low price and widespread availability. Hop on the App Store and get a copy of Mountain Lion if access to Messages is important.