I think that's a misunderstanding of the analogy. The moat isn't about trapping users. Moat as its typically used is to say that a business is protected by the

I think that's a misunderstanding of the analogy. The moat isn't about trapping users. Moat as its typically used is to say that a business is protected by the moat, the prize being the castle/business. The residents/business are free to build and prosper, be productive in other words. When Keller calls it a swamp, he's trying to say there's no castle to be productive in. The swamp makes it a mess, and thus hard for the business to actually maintain productivity. It is still difficult for the invaders to break in (?) but they don't need to...because it's a swamp. They should be busy making a better castle -- which is what Keller is trying to do. Disagree with him or not, but I think that's the analogy.