Whilst you may not be one of the (relative) few who have been invited play Dota 2 in the beta, you can now watch the game using the newly released Dota spectator client. It's free and, as of tonight, you already have it activated on your Steam client.
It's a canny move by Valve for sure: On the one hand, they're able to partly satisfy their legions of fans who are chomping at the bit to get a glimpse of Dota 2 but aren't able to pay the £25 to buy their way into the beta, and, on the other, it's introducing all 40+ million Steam users to Dota as a spectator sport.
Currently, the only way to get a bit of Dota is to either cross your fingers and hope to get invited into the beta or to hand over £25 and buy an early access pass in the store. Considering the game is going to be free-to-play when it does eventually launch a lot of players are happy to wait. I say 'happy', but you should read 'happy' as are biting their nails, writing on their walls in lipstick, and generally going all Ophelia.
So the spectator mode - which has been available to beta players for a while already, and quite impressed Phill - becoming available gives some reprieve to those not much chewed fingertips. It also says something of Valve's intentions for the game. Obviously they want the game played. They're working hard to make it as accessible a form of MOBA as they can. They're rewarding players for being helpful, for training other players, and they're going to come down harshly on anyone who doesn't play nice.
But Valve also want it to be viewed competitively.
Valve have worked on this spectator mode, updating and polishing it, so that people watch Dota. By limiting access to the game with it's closed beta but allowing free and open access via this spectator mode, Valve are fostering an idea of spectatorship. They're catering to an audience who already watch competitive games and they're working to grow it, too. They've released this mode weeks before The International, the biggest Dota tournament yet and their baby.
This also ties into this morning's announcement that Valve are making a documentary about pro-gaming. It's clearly something they passionately believe, that Dota is a sport and they're creating the means for it to be treated as such.
In the blog post announcing the release Valve make a point of saying "We’re also interested to know if you’re running an event to watch The International at your cafe, bar or home. Email us at firstname.lastname@example.org with the info."