I did this earlier today.
I walked around a bit beforehand, and saw some of the challenges they were doing. They had plenty of different challenges. I loaded my phone up (Windows Mobile 6.0 Moto Q) with movie times of the mall I was in, the weather in different cities, etc.
They took my phone beforehand, cleared the cache, closed all apps, etc, so I didn't have anything open to 'cheat' with.
They then showed me their phone, and said it didn't have anything on the homescreen.
The challenge was then to go see the closest restaurants. He just went into the Social tile, and there was the nearest restaurants - while my phone was still loading the browser (lol). Oh well, I was prepared to lose - I used that phone on purpose, and got a WP7 out of it.