"All of these were ideas that seemed bad but turned out to be good, and this is the magic formula for major success." I see this sentiment expressed often, like it's a good thing that you want to pursue an idea that seems bad. If I were to think about founding a start-up, I'd rather find an opportunity that makes sense and sounds good, validate the opportunity, talk to potential customers, and do as much diligence as…
I think you misunderstood the point of "seemingly bad ideas". This is not about ideas that seem bad to you . This is about ideas that seem bad to others , i.e. ideas that seem okay to you, that you probably even verified in the small, but still have trouble convincing others.
Won't a skeptical person find flaw in every idea he is confronted with? In that case, I guess it all boils down to execution. In my opinion, the "idea" need not be very clear but it is okay for it to be filmsy. Building a minimal product with a filmsy idea can help "project" to head in the right direction when you start seeing the facts.
Perhaps, the reason why Google and Facebook succeeded wasn't that the ideas were seemingly bad but "idea" didn't exist in the first place. They just wanted to build something for their own and started getting serious when it got traction.