[ae64]

I don't believe that's entirely true, Facebook has endless channels (e.g. messenger) in which they could introduce or increase their advertising frequency (think Forbes). They could even disclose to end-users that these additional advertisements were being served specifically as they are within the EU, similar to the ubiquitous cookie pop-ups they are already well adjusted to seeing.

[johannes1234321]

If they bring a notable amount of ads people migrate of to snapchat, hangout, signal, telegram, whatever.

[icebraining]

They can increase the number of ads, but it's not clear that it would actually increase their profits.