It's true that you'll have more impact by contributing to a well-known project, but on the other hand the range of activities you can take part in is limited. W

It's true that you'll have more impact by contributing to a well-known project, but on the other hand the range of activities you can take part in is limited. Well-established projects usually don't call for high-level design activities - the sort that a tech co-founder would need to do. They're more about contributing patches and perhaps a new feature (after you've learned the project, which is usually quite big). Ultimately I think you get the same amount of karma if you work on a pet project and not a well-established one. And there's absolutely no reason why the company's sandbox project can't fill a real need and become popular with time.