As to why we're looking at doing this change now, it's being driven by performance problems associated with the current way that the blacklists are used. We're working to speed up hivemind performance, and we found that blacklisting as coded now was a performance problem. So since we needed to speed up performance anyways, it seemed like a good time to make some quick changes to make them opt-in and give each user the choice of how he interacts with those lists.