Firefox suggests an account for syncing and leaked password monitoring, but it's dismissable. Chrome, brand new install, will just take your login to GMail, for example, and automatically use it for syncing without asking.
This is just false. A new Chrome install will not take your Gmail login and use it automatically for syncing. It will prompt you if you would like to use the account for syncing and you can dismiss that prompt just as you can dismiss Firefox's prompt to create and login into an account to sync.
I don't know if it is so now. When the feature was introduced, Chrome synced with my account automatically when I logged in to one of its services. I found it so bold I've never used any Google service inside chrome again.
