With open data, we take the information the government is collecting--again, it doesn't have privacy or security implications--and we simply share it with the public, I would argue, as we receive it.
Proactive disclosure, for me, applies less to data and more to information. It's saying “Okay, we've written some reports. We've made an analysis. We have a proposed policy, and we're going to release that before the alloted time we're allowed to keep it secret runs out or in anticipation of a public debate that we think needs to happen.” So for me, proactive disclosure is disclosing things in advance of when you need to, or just aggressively disclosing information. I would love to see more proactive disclosure as well. I just want to keep it separate from the open data debate, which I think doesn't have the same constraints on it that open information does.