Is it legal to create a website for a product that does not exist without indicating it is still under development?

A widely taught concept, the "lean start-up methodology", advocates to create fake websites and advertisement to accurately gauge consumer demand for a product or service that is yet under development. Is this practice actually legal? To be more specific, are the following legal: 1) I set up a mock up website for a smartphone app that does not exist; 2) The website includes a button with the text "get the app" that links to a survey; 3) An advertisement on facebook invites facebook users to "get the app", and the users would then be redirected to the mock up website Note: Neither the advertisement nor the mock up website include information about the fact that the app does not exist yet. Only when seeing the survey, users are informed that the smartphone app is not existing yet, but that they can help developing the app by filling in the survey. The website is hosted in Germany, but targets consumers across the US.