[jmickey]

It can get tricky. Analysing web performance is not a direct requirement to fulfill orders, so you would need an explicit opt-in from your customers that lets them agree to their personal data being used in this way.

With Mailchimp you probably need to let your customers separately opt into their e-mail being used for marketing purposes, as again that use is not strictly required to fulfil their order.

Same with any other information - your customers need to be aware of all the ways you will use their data. If any uses are not covered by a legal agreement, there needs to be an option to opt-in.

[NicoJuicy]

Analysing performance is a requirement for more sales.