I am not seeing the options in iTunes Radio for "Play More Like This" and "Never Play This" for individual songs, nor the "Variety" slider for each station.
Per iTunes Help docs:
While a song is playing, click near the top-left of the iTunes window, and choose Play More Like This or Never Play This Song from the pop-up menu.
Adjust the balance between new and familiar songs (on the selected station only): Click a station to display its contents, and click Hits (familiar), Variety (mixed), or Discovery (new).
These features are consistently missing across all of dozens of songs on multiple stations. I can't find anything in the Preferences (or the View, Window, or contextual menus) that seems relevant, except perhaps that I have "Share details about your library" turned off. Is it related? I tried turning it on and see no change.
An interesting twist is that I created a station on iOS 7, using an identical starting condition - the name of a band - to one of my existing stations, which has now synced to my OS X iTunes radio, and includes these options. The stations created on OS X have not transferred to the iDevice, however.
1st Created on iOS, appeared on OS X.
2nd Created on OS X, not present on iOS.
Why can't I tell iTunes that I don't ever want to hear "Margaritaville"?!
This is iTunes 11.1 (126) running on OS X 10.8.4