Good point.

You must be sure to PLAN for the impact you want. If you want to reach a lot of people, going to 40 small events is probably the wrong plan.

But even before that, you have to collaborate with marketing, product management and biz to figure-out what impact DevRel needs to prioritize. Is it driving awareness of products to help stimulate trials/sales? Is it building relationships with specific community thought leaders? Is it establishing 1st party thought leadership? Is it helping customers be successful implementing (to Paul's point)?

If there is a shared understanding across marketing/product/biz about what impact DevRel is pursuing, that helps a lot when it comes time to measure.

And maybe that's the biggest point: DevRel goals/metrics don't mean much if the product/business they're supporting are not trending in the right direction. 

Having lots of followers, speaking at big events, and all the good stuff DevRel does should be a means to an end that benefits the business. It's easy for DevRel teams to spend too much time doing things that benefit the Advocates more than the business.

HOW DO YOU KNOW IF YOU GOT THE VALUE?
Two ways, in my opinion:

1) Direct measures: This is the classic, inside-out DevRel measures like attendees, eyeballs, 3rd party surveys for mindshare/awareness, social media, etc.

2) Indirect measures: These are the (ultimately) more critical outside-in business metrics DevRel activity is supposed to be influencing

If DevRel gets an "A+" on Direct Measures, but the Indirect Measures haven't moved the right way, DevRel should still think critically about what it should change/do differently. Maybe it means DevRel needs to collaborate more closely with marketing.

If DevRel gets a "A+" on Direct Measures, and the Indirect Measures are showing some lift, it's a gold star for DevRel. The more directly DevRel can link their KPIs to the business KPIs they have impacted (like showing a big spike in downloads after producing a webcast), the bigger the gold star.