"Assets under management" is a vague term used in the business world, and because it's a business term many people gloss over it. Many people think of Blackrock in terms of pension plans. (along with Vanguard). When non-business people discover that AUM can consist of entire corporations-- especially in banking, media, and phameceuticals-- they will be shocked at the degree of control Blackrock has over them.
As an example, we're led to believe that cable networks such as CNN and Fox are rivals; in fact, Blackrock owns enough of each to dictate what they present their viewers. In that regard, it's like professional wrestlers fighting each other in a match; both wrestlers are part of the same organization, so an hour later they party hard with each other at the corporate party.
Extend this to other AUM, and it can be enough to get the people marching to its global headquarters with torches and pitchforks.