Ben Miller from Sniff WiFi comments:
By this point my Chromecast was already acting as a client/station (using a different MAC address) to my home wireless router. What seemed to be happening (and when I say, “seemed to be,” that’s carny for “I saw this, but I need to investigate further before I make a conclusion) was that my iPad was stubbornly trying to stay associated to the Chromecast’s BSS, and the Chromecast wouldn’t shut down the BSS until the iPad got off. I’m guessing that it has something to do with running the Chromecast app on the iPad.
I’m a sucker for packet captures. Especially for “automatic” devices that don’t really dive into their inner workings. Read up for the scoop on how Chromecast really behaves.
Read more at: A Fish in the Desert: Chomecast, Sniffed