To me it seems that Steem should always show ways that their own coin can be showcased. In this case selling advertisement. Using another coin seems counter intuitive. Someone that is interested in Steem and is thinking about buying some, seeing that steemit.com utilizes BAT would give me the shivers. Hell, as someone that already purchased Steem it would still give me the shivers (and maybe more rightfully so than with the former). Then again, it might just be me