BlackRock (BLK) CEO Lawrence Fink recently fired off another one of his annual letters to top CEOs of publicly-traded companies -- this time, targeting activists. The Deal senior editor Ron Orol details the letter, which raises concerns about short-term pressures on companies from activist investors. Orol explains that Fink is not completely negative on activism in the letter, as he cites that some activists take a long-term approach. However, BlackRock is still more supportive of activists than you might think, according to Orol. The company actually has a list of activists that it likes and doesn't like, he says. Not only that, but BlackRock has been more supportive of activists than two of its rivals, according to a recent Houlihan Lokey report.