We don't want anyone on the platform who isn't aware/comfortable with it. Our instructions to the websites (when they join) are to create a link to the opt out page. I supposed it could be a direct opt out
It isn't as much a matter of ability to verify, but to enforce. Currently the platform is supplied by quite a few websites (over 100), and the best way to get them to adequately communicate this is through proper incentives.
The incentives must be: if you do not comply, your content won't be monetized (as would happen with ads).