There will be many carefully phrased altruistic thoughts about downvotes, but in the end they will be used as both a valid curation tool and as a weapon just like on every other platform. You should proably use downvotes sparingly, because they can hide a post from view, take profit from someone, and make enemies.

The courtesy of a comment when downvoting is expected but not required. 1 downvote can currently hide your post. I have been downvoted for politics multiple times already, with a few of them clearly being just to hide my point of view from other viewers. The use of downvotes for politics will continue to get worse until something is changed to make it more obvious or difficult to use as a weapon, just like on all the other platforms.

My only advice would be to not downvote the top 100 steem holders, and take specific care not to discuss anything political, funny, or not-PC with them either. (if you want to stay visible and make any money...)