Thanks everyone.
I’ve made up my mind in that it’s okay for me personally, for a couple of a reasons:
- I cannot use the analytics mentioned to compromise your privacy or anonymity as an individual
- I have no monetary incentive to include the analytics: I provide resources/information for free. If you can’t find what you’re looking for on my websites, that is a disservice to you and me
- I have whitelisted domains for analytics providers I’m okay with
As for making them opt in: you can barely get someone to opt out, and if you do, the method is obtrusive. I see no way of making analytics opt-in and unobtrusive in a way that does not render them useless.