Andrew Ross Sorkin, author of the definitive financial crisis tick-tock, should know what a firestorm is. But when he says that an anodyne letter from BlackRock’s Larry Fink “is likely to cause a firestorm in the corner offices of companies everywhere,” you have to wonder.

Fink’s real clout comes not from his active portfolio, but rather from the trillions of dollars he oversees in indexed ETFs. And there, as Fink himself admits in his letter, his hands are rather tied. In those funds, he writes, “BlackRock cannot express its disapproval by selling a company’s securities as long as that company remains in the relevant index.”

So, what is Fink doing? Sorkin seems to think that he’s upping his activist game, voting against companies’ preferred directors more often, and generally throwing his weight around a bit more often than he used to.

An important point is the new thing which Fink is talking about in his letter. Instead of just engaging with companies in the middle of proxy fights, he wants to talk to those companies, and their board members, on an ongoing basis, and ask them questions about their strategy and sustainability. But the big unanswered question is: Will all those meetings actually change anything?

On an individual case-by-case basis, it’s going to be hard if not impossible to find any specific company which changes its ways after a meeting with BlackRock’s “investment stewardship” team.

On the other hand, on a global basis, the sheer weight of all those meetings, with all those CEOs and board members, might just nudge a few close board-level decisions one way rather than another. We’ll never know the counterfactual, of course, but it’s likely that simply talking about social issues with big shareholders will subtly change board members’ priorities somewhere.

Read the full article about Blackrock by Felix Salmon at Cause & Effect.