Looking back at YouTube, PayPal or many others (now) most successful companies, their originally idea was completely different. PayPal changed 4 times during his first year, YouTube at the beginning was a video dating site. So, I think that another way to build huge companies is more in the ability of the founders to understand and iterate on first early adopters needs instead of "I need that" scenario. They have to be as fast as possible to change the product around what people want. But if they are fast enough a startup that looks a completely disaster at the beginning could turn into a gold mine.
Thinking about Slide; Max Levchin has changed the company proposition many times, or look at Airbnb, they were a renting couch website with the focus on the events and not on travelling, they changed that very fast and now they are just making a revolution into the world of travel.
The most important part, is to start, with the conscience that your company could change completely, and you have to accept that before it will be too late to fit the market.