What is the test for applying a de novo review to the question of whether a transaction was usurious?

The application of the law to a set of facts is also subject to independent review when the issue "can have practical significance far beyond the confines of the case then before the court." (Ghirardo v. Antonioli (1994) 8 Cal.4th 791, 801 [applying a de novo review to the question of whether a transaction was usurious].) The rationale is that "[i]f such questions were effectively removed from the consideration of the appellate courts, the development and clarification of . . . important issues . . . would be impeded." (Ibid.)