I'm always mindful not to boil every hypothesis or riskiest assumption I hear into a landing page experiment. There are so many creative ways of varying fidelity to test the riskiest part of your business model.

That said, MOST of the time - these days, the riskiest TYPE of risk is market risk (as opposed to technical or financial risk) and the idea usually breaks down somewhere on the customer journey map, often at step one. A landing page (hypothesis page) it is one of the most useful tools I know of for learning in what we call at the Pearson Product Lifecycle, the "EXPLORE PHASE".