Although you may think it is just me and my hubby and boys it probably isn't. Your neighbors, someone on the street, anyone going by with a wireless card can see your wireless signal, and connect to it. Once they are connected, all they have to do is find their default gateway and type it into an internet browser and it will redirect they to your wireless router configuration screen. There are even programs that will eliminate the only small steps that are inbetween finding the address they need to connect to.
If you don't haveany password set, they won't even have to try to guess. They can then set up mac filtering or encryption themselves and block you out! They could do anything they wanted is my point, so even if you don't want to mess around with WEP or MAC authentication, set a password on your router!
The other problem with not encrypting your data is you make it that much easier for the black van sitting outside your house to get your credit card info when you send the data through the air. Sure there are other layers of encryption, but without your wireless being encrypted, its that much easier. People that commit identity theft and steal credit card numbers are looking for people in your situation to take advantage of. I am aware I may sound a little paranoid but it does happen.