Question: Assuming that feature flag toggles are a good idea, and should be implemented into code that developers write. For example Etsy swear by them as a [major part of their culture](https://codeascraft.com/2011/02/04/how-does-etsy-manage-development-and-operations/).

**What is a good way to persuade (and enforce) developers to start using feature flag toggles?**

More information about feature flag toggles is explained in [Q: How to use feature flag toggles](https://devops.stackexchange.com/questions/162/how-to-use-feature-flag-toggles), [Q: What are feature flag toggles](https://devops.stackexchange.com/questions/344/what-is-a-feature-flag-toggle-and-when-to-use-them-or-not) and very extensively in Pete Hodgson's [article on the subject on Martin Fowler's blog](https://martinfowler.com/articles/feature-toggles.html).

Answer: 
Developers (and usually development managers) usually look for two outcomes associated with framework: ease of management, and speed of deployment. You want to ship code faster, and easier.

Provide evidence that the approach works; try building a small POC using feature flags versus the old way. Case studies matter less to tactical people (developers\engineers) than strategic people (middle management\product designers).
The rationale to have feature toggles is not something for developers to decide. This is something for product owners to care. Developers enable this change in the most sustainable and safe manner. I critique this very question.