The anonymity is within using several addresses. Just use more than one.
Incorrect. Users can use taint analysis to establish a link between the few addresses. If the user
accidentally spend inputs in two different address in one TX, it would be a clear indication of their link.
Accidents happen, but never likely. Using multiple accounts, wallets, VPN'S and so on will give you a ticket to making sure your identity is safe. Not to say that I do this but if anyone was to do this then it'd be completely effective. Even via PayPal, you can be anonymous if you don't actually link your PayPal to your bank accounts. I never did, and I was still able to make payments for things with people who kindly accepted PayPal.