I dont see the point of the steambox. If people want to use steams big box feature they can just build a small form factor pc using a mini itx board. or even get a shuttle.
Yes they could do that. This is just another option available and not everyone wants to build their own system. If they make these Steamboxes look really cool and the gamepad is good then they could be popular. Theres a lot of BUTs at the moment.
As I have said before the most exciting thing for me about this is that Valve will be using their own OS SteamOS which is based on Linux, they have declared war on Microsoft, if they succeed this could take away their dominance of PC gaming.