For learning to happen, all that's really needed is a learner to ask questions, engage in some hands-on activities, and have a space to document and reflect on the process. Everything else isn't really a learning issue; it's an assessment issue. For too long, we have allowed assessment to drive how we define learning, instead of the other way around. The thing that gets me excited about badges is that it has actually put focus on the value of informal learning because Badges have the potential to provide a uniform way for people to understand what occurred within the informal learning process. Badges provide a greater degree of context to the informal learning process, largely by including the organizational reputation of the issuer as part of the value/credibility of the badge.
The Badge Specification is relatively lightweight, and it should remain that way. Badges alongside a portfolio system, however, provide a context that raises the credibility of both the badge and the portfolio. The work highlighted within the portfolio provides additional information about how and why the learner earned the badge. A well designed portfolio system, working alongside a well designed badge system, would collect these pieces as learning occurred, so the accumulation of artifacts for the portfolio is indivisible from the learning itself.