If there was a password on the router that means it had encryption turned on out of the box, my sky broadband had the same. That in itself has shown that the OEMs/distributor are getting a bit wiser. There are two forms of possibly wireless secruity WEP and WPA.
A long time ago (not sure exactly how long) WEP was cracked, this meant that anyone with a wireless card that had some specific features could monitor a encrypted wireless network and after inspect all the packets could figure out the key and reverse it. This means that any half competent nerd can crack a WEP network, the more traffic on the network the faster you will crack it. There is kind of a sport of cracking them around major cities called wardriving. I think I even heard/read some story of some guys in new york with a helicopter and a high power antenna to boost their wireless adapters
WPA, as far as I know (i just know enough networking to get by) hasnt been cracked and is pretty much secure.
The fact that your router came out of the box with security turned on is a response to the exact issue being discussed here.
ETA: keybored your comparison is pushing it a little bit as the person also using the connection has the ability to decrease the owners bandwith and therefore depriving him of something, which as someone pointed out earlier is the legal definition thats worked with.