The International DOTA 2 2012 is one of the humongous gaming tournament which is being held in Seattle, USA. Valve corporation is organizing this tournament and they already have a vast experience of organizing this type of tournaments as they carry one of the most popular game Counter-Strike under their belt.
Most of DOTA 2 fans are physically present at Benaroya hall to experience this event live. But those fans who are willing to watch this tournament online they can easily stream it online. You can watch DOTA 2 The International 2 Live stream with commentary by TobiWanKenobi.
Note: Just click on the stream and wait for couple of minutes for this stream to start.
If you are facing delays or lag in the stream above, its just because of the load and traffic which is coming from all around the globe to watch this tournament online. The solution of this problem is to install the Dota 2 Spectator client on Steam which will fix these issues.