Pandora for iPhone Security Flaw?

Recently, I restored my iPhone fresh, didn’t restore a backup or anything. I installed the essential apps I use, and one of them was Pandora Radio.

To my surprise, when I opened it, all my stations were there and it was like I didn’t even have to login. Weird, I thought, well maybe the full restore left some setting on it or something, no big deal.

Now, a second incident. My old 2G iPhone, when I gave it to Emily, was wiped clean, clean, clean. She has a few apps, but this morning I was like, try Pandora. So I install it on her phone, open it, and woah, all MY stations are listed, and it is logged in as me. WTF?!?!?!

My only guess is that it somehow ties to the iPhone hardware, since months ago when I was using the 2G phone, I had loaded, not sure how, but yea, there is definitely something going on.

Wondering if anyone else has seen an issue like this?