Unfortunately the tools for this aren't as nice as they should be. For example Google Voice sort of intentionally makes it difficult to use them as an anonymizer. eg. you can't have a GVoice # that doesn't correspond to a physical phone, and it's a pain in the ass to dial out with your phone and make it route through the GVoice # so that people see that number in their caller id.
Similarly, to sign up for things you often have to give an email that they check, so you can't just make one up. Ideally you would be able to give a temporary email address, which routes through to your real one for a week or so and then expires. Email providers could easily give this to you (and just limit the # of outgoing mails to prevent spammers from using it). But they don't actually want to protect you from advertisers.