Itunes match question

On your computer yes, you can just double click the song to stream or just click the cloud icon to download.

On your iPhone, iPod Touch and iPad no, iCloud forces you to download each song at this time. However it allegedly auto removes songs for you after a certain time being on your phone without being played.

Note that it's very easy to go to your usage screen and delete all music on your iDevice at the same time, or from the music app, delete individual songs, albums or artists.