I can think of two reasons to avoid licorice. First, as Lotus pointed out earlier, it has the side-effect of inhibiting 11β-hydroxysteroid dehydrogenase type 2. This increases cortisol in some parts of the body which can increase blood pressure. Elevated cortisol is part of how stress kills people, so I still wouldn't feel safe even if my blood pressure was still normal while taking it. (Licorice doesn't affect the type 1 dehydrogenase, so it isn't a substitute for corticosteroid drugs.)

Second, glycyrrhizin blocks gap junction intercellular communication. Gap junction intercellular communication allows healthy cells to stick together and inhibit tumor proliferation. Improving gap junction communication is believed to be one of the ways that vitamin D prevents cancer, particularly breast and colon cancer. 1 2 3