[Nextgrid]

For analytics try to use self-hosted solution or even rely on your existing logs (if a feature is hitting endpoint X and you want to know how frequently it is used you can just grep for that URL).

If you really need to use a third-party, I'd prefer one where you pay for the service (MixPanel, etc) rather than a "free" one like Google Analytics. At least the paid one has less incentive to use the data for their own purposes while the whole point of Google Analytics (and the reason for it being free) is to provide data for Google's advertising business.

[kylerpalmer]

Do you have an opinion about situations where 'tracking' is really what is needed. For example, keeping track of a referral from a partner, so that you can pay them for converted customers?

[Nextgrid]

In this case, on the web, there is already a solution which is the Referer HTTP header (https://en.wikipedia.org/wiki/HTTP_referer) - it allows the destination web server (and no one else) to know the referring page, as long as both are served using the same protocol.

If HTTP referrer isn't an option, a custom query parameter like ?referer=source_site is what I'd consider okay - it looks straightforward so someone can decide to remove it manually if they have a good reason to do so. I would avoid stuff like utm_ parameters as they just mean Google Analytics and not only is this blocked by default by my browser & DNS server it also means you don't care about my privacy and are happy for Google to track me (I never click on links in emails for this reason because they all got some kind of scummy shit to track me that involves a third-party).

[ziddoap]

Are you paying a flat rate per conversion or a flex rate based on customer spending or some other metric?

If its just a flat rate per conversion, this could be accomplished with minimal (if not no) PII collected from the customer.

[kylerpalmer]

Ongoing based on revenue. Most PII is in our payment processor, and never stored on our servers.