The like and dislike options are grayed out. I'm on an iPhone 5s and iOS 7.0.
According the Apple support doc for iTunes Radio:
There may be some DJ-curated stations that you may not be able to modify. You can't like or play more tracks like this while listening to some DJ-curated stations. You can however, start new stations based on the current track or artist of a featured station or add tracks to your iTunes Wishlist from the Star (✭) menu.