Its concern is mapping the tweets (data) into a view (another form of data). That is one concern. If you like, you can split it into smaller functions (since everything is referentially transparent, unlike in MVC), but that would be overkill considering the given example.
the point i think is scope injection makes controllers clueless about any view responsability. That's a powerfull idea. Well they are not totally clueless because one still needs to "force update the view" sometimes in Angular ($scope.$apply),but this can be avoided by using Angular promise api.
