Ned went through a lot of trouble to tumble Steemit Inc's stake through the exchanges and to random accounts. Anonymity only works if you stay anonymous. If Justin starts using that stake to replace witnesses it's going to be really really obvious which accounts he controls. We'd then be able to fork all his stake to @null and he'd look like a complete fool. Guy better tread carefully.

This point might be moot though considering 42 million coins are still on the @steemit and @steem accounts. Simply forking that stake off the chain right now preemptively would be the likely smartest course of action... of course stealing an investors money is really really bad publicity for everyone involved... so dire action like that can't happen without the immediate threat of a hostile takeover.