Ever stood in the aisles of Sephora trying to remember the name of the shade of foundation you always use? Or in the aisles of Walgreens with instructions from your boyfriend to buy him a new stick of deodorant, but can't remember what brand he uses?
These things you see every day aren't necessarily all things you commit to memory, but with your cell phone, it's a nonissue.
Before hitting the drugstore or department store to replace an empty makeup or other toiletry need, snap a picture of whatever detail you tend to forget. Then at the store, your preferred brand, variety, or shade is right at your fingertips.