I support such laws too, but I wouldn't expect them to really change this. I think what we're seeing is more of a monopoly problem than anything else, even if violating privacy is a part of how they pull it off.
It's very hard to prove that a company that does, in theory, have access to data is not storing it or looking at it. Even accidentally. I just finished explaining all this to someone who freaked out about a Facebook post they saw about how Facebook was starting to collect information about everything you do off-Facebook. I had them show me what they meant, and it appears to just be every app that integrates with Facebook comments or allows Facebook sign-in as an option, etc.
The problem is one Facebook naturally got because of it's success: everyone has good reasons to want to work within their ecosystem. So they get tons of data on everyone. You can inconvenience yourself and refuse to ever visit a service that might share data with Facebook. But honestly: who's going to find that practical and do it? And if Facebook ignores the setting and "accidentally" captures all this data, and I suspect they're misusing it, how do I really get an investigation and more than a slap on the wrist for them?
It's messy to be a platform that provides a service and a consumer of that service that competes with your other consumers. At a previous job of mine we made a conscious decision not to do that for fear it would hurt our core business to ruin relationships with our customers. The problem here is Amazon just doesn't fear that. And I can't say they should. But the root problem seems to me to be more of a monopoly problem than a privacy problem.