Interesting news have recently come out from Pavel Djundik, the creator of SteamDB. The invaluable website that archives and displays just about all the possible data that you'd want. From concurrent player numbers, to game repository updates, and price history.
Needless to say, he's probably one of the best sources you could ask for, and according to Djundik, we might soon be able to record clips while playing games on Steam, just as easily as you can capture and share screenshots.
Not only that, but supported games will also support special timestamps that highlight various game events, with a hero kill being used as an example for Dota 2.