One of the most annoying things about open source is you have absolutely no idea who is using your stuff for what unless it breaks.

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This seems to be a big unfilled niche. There should really be a good common system for collecting and reporting aggregate statistics about features and users, that library and application authors can use to guide decisions.

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I know of a number of existing open source projects that actively collect usage metrics, but these tend to be ad hoc, heavy-weight, and specialised to the project in question:

**Package installations**

* [Debian Popularity Contest](http://popcon.debian.org/)
* [Stats for Bower](http://bower.io/stats/)

**Feature usage**

* [Chrome Platform Status](https://www.chromestatus.com/): [CSS metrics](https://www.chromestatus.com/metrics/css/popularity), [JS/HTML metrics](https://www.chromestatus.com/metrics/feature/popularity)
* Firefox Health Report: [blog post](https://blog.mozilla.org/metrics/2012/09/21/firefox-health-report/), [FAQ](https://blog.mozilla.org/metrics/fhr-faq/), [support](https://support.mozilla.org/en-US/kb/firefox-health-report-understand-your-browser-perf)
* [Firefox Telemetry](https://telemetry.mozilla.org/) ([wiki page](https://wiki.mozilla.org/Telemetry))


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A good model for how easy integration should be from an author's perspective would be something like [Sentry](https://getsentry.com/) ([example integration docs](https://docs.getsentry.com/hosted/quickstart/#pick-a-client-integration)).

Perhaps what's needed could be described as "Sentry for feature usage metrics"?

In fact, although Sentry is primarily aimed at error aggregation, it seems very close to being a good fit for this: perhaps it can be extended to allow for good feature usage reporting and metrics, too?

(If not, it can at least serve as design inspiration.)