Obviously AS has to have your ID and password to bid on your behalf. At the end of the day they are a business so if it gets out that they are leaking/selling/abusing their customer's passwords then they're not going to stay in business very long. When you add your password to the AS system it is via a secure page (ie. http
s and the padlock at the bottom of the screen) so that stage is secure. One can only hope and assume that passwords and IDs are then stored securely on their system...
Ultimately the choice is yours - AS (and other sniping services) are biding on your behalf - if you want that to happen then you have to trust them with your password.
R2