Are storefront sites like eBay, Apple App Store and Amazon considered to be "web applications"?
The current help page is pretty vague, it just defines a "web application" as "a website which behaves like an application" without really defining what an "application" is. The Wikipedia description of "application software" tends to describe it as doing complicated or constructive tasks such as a word processor, a spreadsheet, an accounting application. In the old days storefronts were generally considered to fall into the category of E-commerce portals, not applications, however this site may want to make a broader definition of "application" that includes relatively simple functionality. For example, a hotel web site that allows a visitor to book a reservation. Is that an "application"? What about a club web site that has a form that allows a person to enter their email address to be added to a mailing list. Is that considered to be an "application" even though all the user is doing is entering an email address and pressing enter?
In any case, I would suggest that some kind of definition of what constitutes an "application" for the purpose of this stack exchange should be included on the help page.