You can be all designer, or all developer. You can be mostly designer with some developer, or mostly developer with some designer. Hell, you can even be the golden unicorn of Web workers everywhere if you’re half-n-half (or just both?). Most of the best designers and developers I know are all over this spectrum.
Designers and developers—like any other group of people—shouldn’t be pigeonholed into separate roles. Doing so is damaging to individuals, your company, and the entire industry. Quality products and cultures thrive on employing people with a broad set of skills and at least one specialization. Embrace the sliding spectrum of skills.
I typically think of myself as a designer, but I spend most of my time writing code. Does that make me less of a designer? No, that makes me more knowledgeable about the medium I work on. Any experienced worker from nearly any industry knows how paramount that can be. Know your craft—it’s goal, medium, impact, and end product.
Bottom line? Get talented people together that can have fun and ship awesome shit, and good things will follow. Don’t worry about the labels.