If you have a "Send anonymous usage statistics" checkbox in your application, should it be enabled by default or not? If you have it enabled by default, you will probably get more statistics, but some privacy-fanatics might get angry.
So should it be enabled by default or not?
No. Always allow the user to opt-in.
You could prompt the user the first time the app is ran, with a message explaining why it would be a great idea for them to join, but I would default off.
Automatic opt in causes the PERCEPTION of your app to be "shady" for some people. This perception has a big influence on the total UX.
And what's more - this can, and will, extend to other apps you write - potentially loosing other future sales.
Make your app above-board, and you'll have more people using your app - even if fewer people opt in, you'll get more data.
It should not be, this is one of those situations where you go to the core principles and do what's right for the customers. In long term sticking to the core principles would add tremendous value to business, but if one deviates, it's a slippery slope. Be the voice for customer.
Still, the data is valuable.. see how you can encourage users to accept it... Tell them their privacy is safe (if it truly is), tell them what's in it for them - it'll help us build better solutions for them etc. Don't just treat it like a functionality, but as customer communication - humanize it.
Opt-in is far better than opt-out for user perception - and probably regulatory issues as well if you are in some region (e.g. EU) which has strict privacy and data protection standards. As Don Nickel pointed out, negative perception is a likely result of sneaky default-checked prompts, I can attest that personally I am far more suspicious of such sites or programs. Of course, it also depends on your audience and can be permissible in specific cases.
There's an article on leaving opt-in unchecked being a better option at Nielsen-Norman site: http://www.nngroup.com/articles/mailing-list-usability/. Depending on your application's use case, their Request Marketing article might help as well.
Opt-in required per GDPR regulations.
Privacy by default: https://www.ics.ie/news/what-is-privacy-by-design-a-default
