a dearth of possible keys
the 2wire 1000 series of broadband 'modem'/wireless router, which includes the 1800HG, the standard one recommended by bt for their broadband, comes with 64-bit/40-bit WEP encryption set up by default. the default SSID (network name) is "2WIREXXX" where XXX are the last 3 digits of the serial number, and the default WEP key is printed on the bottom of the unit.
the interesting thing about this is: 64-bit WEP uses a fixed 40-bit key which is a network setting, and 24 extra bits which are constantly changing with each message sent. a 40-bit key works out to 10 hexadecimal digits, ie digits 0-9 or A, B, C, D, E or F. but the default key printed on the bottom of the box is a 10 digit number which only uses decimal digits; ie 0-9. this means instead of about 1 trillion possible keys, there are only 10 billion.
given the well-documented, inherent flaws of WEP encryption, (ie you can find out the key if you read quite a few packets and get a little bit lucky), this seems rather bizarre..