I'm not very familiar with the space yet, but despite a weak attempt to argue something along the lines of "nobody cares about your idea," this ultimately reads to me like "Don't ask for an NDA, because it would inconvenience me if I decided I wanted to build my own business based on your idea."
That's a legitimate concern though. People have unoriginal broad ideas ("I want to sell stuff through app/website") and supply over-reaching NDAs ("_everything_ mentioned is covered, with no expiration date"). Even if such is ultimately not enforceable, it could still be a major legal pain, if during your lifetime you get to work on a project that also implements some type of "selling stuff online" (see Lodsys' troll patents and legal pursuits).
