[Silhouette]

Why would they allow someone using the service if they didn't get something back?

That's a good question, but once GDPR is in effect, the law is going to require that all consent is genuine, informed, active consent. A consequence of that is that someone must be able to withhold their consent without suffering for it, unless the thing they're consenting to is essential to whatever else they're doing.

If you're thinking this fundamentally undermines the current business model of sites like Facebook, you're probably right, and given the political rhetoric around the GDPR, it's possible that this was the intention of the EU from the start.

[wbl]

Ad revenue is essential to Facebook running. My guess is that FB will continue to work even without this other data just given what they know on the site.

[Silhouette]

Ad revenue is essential to Facebook running.

Ad revenue may be essential to Facebook being commercially viable, but it's not required at all to provide the social networking features that users actually want.

My guess is that FB will continue to work even without this other data just given what they know on the site.

But if they have data acquired with users' consent for social networking purposes, they won't be allowed to process that data for purposes such as targeting ads without consent.