(SkypeAssets ) An update to the Skype terms of service late last year spilled the beans that the feature was coming.
Skype Begins Testing Video Messaging Feature
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FEBRUARY 15, 2013
Ina Fried, AllThingsD

Skype has started allowing some users to send short video messages to one another when their friends aren’t available for a live chat.
The Microsoft-owned service had said the feature is coming. Starting Friday, those with the latest version of Skype for either Mac, Android or iOS can send the messages (users of Skype on other platforms can still receive video messages.)
Read more: AllThingsD