I like giving these "services" a one off email address from my own catchall and then check in on it months later to see how they attempted to monetize the data. Would probably make an interesting time series info-graphic.
I do that with marathon entries. The worst offender by far has been the Rock N Roll series, who sold my email (runrocksoldthisemail@example.com) to several races throughout California. I chuckle every time something occasionally comes in to that address. 9/10 would recommend.