eBay usually just implements them on an account, with an option to opt out (I have them on this account, but not my other, older account) - there is an opt in link, but so far I don't think anyone who hasn't had eBay force it on them anyway has been able to opt in. A lot of sellers have had it implemented on their account but then not been able to use them, opt out or actually list anything, so there are definitely some issues surrounding all that stuff.