If you need to keep notes or addresses, the best way to do it without losing it is to type in the message and SMS yourself, or if it's the home address of your friend or maybe even the address of their office, simply type in the address and SMS to their phone (via the phone book) and while the phone is trying to send, press the NO button to cancel the operation (you don't want to pay your service provider (SP) for that SMS, and you don't want your friend wondering why you SMS their address to them).
This way, if you needed their address while you are on the move, you do not need to search for that piece of paper you put into your pocket nor to on your laptop to find their address. Simple look in your Unsent messaging menu under their name to find the address. This can be very handy while you are traveling abroad. It's easier to find the address in your mobile phone than a piece of paper you wrote a few days ago and kept it in your pocket.