An article from Dan Larimer was quoted by founders on BCT thread at pretty early stage, so one could have guessed Dan has something to do with that project. But sure there was no direct announcement until the very late stages of early mining... Everything related to early Steem is like that - lots of hints were made, but nothing said directly. A lot of FUD was around too, so it was hard to know anything for sure.
Been there, mined that, posted a lot on that thread on BCT back then :). And of course, I still regret mining too little at that time.