I’m using Google Analytics. This tells me how people get to the site eg from Facebook or a slot racing forum. That’s really useful because it helps me know which social communities are most interested in what I’m doing here so I can do more like that. It also lets me see things like how long people spend on the site and which route they take through it. All this data is anonymised.
I’ve also got some Google code on the “thanks for signing up” page that you see when you send your name and email address. This tells me how you found the site which is essential to help me target my limited budget wisely. I’m using Mailchimp to manage my email list beyond them I have no intention of sharing your details with anyone.
So thanks for your understanding. If you want to opt out you probably know how to already but if not there are plenty of ways to do so!