I just noticed... if you have AdBlock Plus installed... WebApp Builder will not load. It gives the error saying the Share widget config.json could not load. And the Sad Face. End users will not have an idea what this is or what the cause is.
Solution: following the approach of many News sites, which detect if an Ad blocker is on, and recommend appropriate action for the users to take, to proceed. (a memo about whitelisting the site or turning off the blocker, even sometimes including a movie (ani gif) showing how to move the cursor up and disable it; this could be custom-tailored to be browser specific, in order to show the right movie to the user, for their browser, based on their browser agent)