An excellent article detailing the homogenisation of magazine covers:
"Take a look at your local newsstand and here’s what you’ll see: racks upon racks of magazines that look almost identical. Whether they focus on music, fashion, cigars, fitness, women, or men, most magazines typically feature a grinning celebrity on the cover peeking out from behind squadrons of coverlines. It wasn’t always like this."
The article then follows this up with some real world examples.