2 iPhone households, be careful with iCloud
The wife and I have both been using iPhones for a couple years now. I get a new model and pass my older model on to her. I don't always buy the latest model, it just depends. So I've been using the 3GS about a year and decided to go with the new 4S. Bought the 4S at and Apple store and then went to a nearby AT&T store to do the SIM card dance. All appearded good. I enabled iCloud on both phones, without fully understanding what could happen. The wife and I both use my iTunes account for our periodic purchases and it turns out that iCloud uses that same account info. The wife complained about all my extra contacts she had now that she was using my old 3GS. She began deleting all those contacts that she didn't recognize or want. Well turns out when she deleted them on her phone, they were also deleted on my new 4S phone!!! Since iCloud was turned on for both and since iClould uses the Itunes account info, it was working to keep the contacts list the same on all my devices. Just a word of caution. Either create a new iTunes account for each user or disable iClould on one of the devices (which is what I've done for now).