Ok I havent read all this thread only the first page but here is my 2 cents on why you should ALWAYS secure your wireless connection.
1 - If someone becomes part of your LAN and goes out via your public IP, then any activity done illegaly will point back to your public IP. It would be very hard, if not impossible to prove someone else was on, and especially who that person was. Therefore your public ip could be used in a DDOS attack, used to look at child porn etc etc, stuff you dont want your ISP to associate you with.
2 - lets say you leave your wireless unsecured OR secure it with WEP which as far as im concerned might aswell be the same thing since wep is so horribly insecure, if someone becomes part of your LAN they have access to your router, providing your using a password of over 7 characters you'll generally be safe from a practical brute force, however if your leaving your network unsecure chances are you've left the password as default or just left it the same. If an attacker gains access to your router they can do several things - a. Change your DNS settings to a poisoned DNS server - all the attacker needs is BIND or some other dns software on their system, point the DNS from your router to use the attackers local ip, all DNS requests will then go through the attackers system, he/she could then easily add bogus records for sites like paypal/ebay etc that are imitations that will drop your details into a database once there entered.
b. Generally screw around with your connection settings, particularly annoying if your on ADSL as they could start changing your VCI values and your ADSL will stop working without you knowing why.
3 - arp poisoning - an attacker could easily identify himself as your gateway peforming a 'man in the middle' attack, he/she could then monitor all traffic coming in and out of your computer. this is obviously something you dont want, while most sites where you login to will use https and therefore your details will be encrypted, everything else is sent over plain text (including most pop/smtp authentication details)
ok theres probably many others but ill leave it at there for now. Personally I think leaving your wireless network open is a very silly thing to do and just asking for trouble!
