I think the fact that the focal point of content here is on the user and not something more broad like a subreddit helps each user get what he wants from hubski without imposing on anyone else. So while a subreddit might one day become flooded with subpar content, I don't expect someone who has consistently posted great content to suddenly start posting memes and image macros. The responsibility lies on each user instead of the community as a whole to generate likable content, so the scope of quality stuff coming in has a much narrower focus. At least, that's the theory.

They would probably shame the USA's obsession with military defense and terrorist hunting, and how we spend a disproportionate amount of time and money on those endeavors than we do on scientific funding. Of course, there are plenty of people saying that now -- just as there were probably plenty of people decrying 19th century racism -- but the minority voice of reason tends to get drowned out until it becomes the accepted view several generations later.

On a lighter note, perhaps they will find it quaint (or horrifying) that people used to drive their own cars. Maybe one day I'll tell my grandchildren of a time when huge box-like machines rushed by each other on massive expanses of concrete, separated only by painted white lines and contained by crude metal guard rails, killing a million people a year in fiery collisions caused by human error. Additionally, they ran on fossil fuels and pumped out poisonous gases from the rear. Almost everyone owned one!