I wouldn't be surprised if both are illegal. But these days, the correlation between "X is illegal" and "larger org's do not do X" just ain't what it yousta be.
My understanding is that it's legal with opt-in, but the opt-in is allowed to be confusing, opaque, and sticky, so most people "consent" without informed consideration. We really need to revisit contract law in a modern context. Call me crazy but I don't think it's reasonable that our society operates in such a way that easily 90+% of people are subject to contract terms they signed but don't know or understand.
My understanding is that it's legal with opt-in, but the opt-in is allowed to be confusing, opaque, and sticky, so most people "consent" without informed consideration. We really need to revisit contract law in a modern context. Call me crazy but I don't think it's reasonable that our society operates in such a way that easily 90+% of people are subject to contract terms they signed but don't know or understand.