Good question. It might be a difference in degree rather than a difference in kind. Consider the social media space: if you want to build a Twitter clone, you could do so in a pretty short amount of time with a pretty small team. You could buy ads to get everyone to know your product's name. Those ads will bring in enterprising early adopters, but no matter your ad spend or the quality of your platform (you could even include an edit button for pete's sake--and for free at that!), you're very, very unlikely to unseat Twitter. The reason is that Twitter's product isn't its platform or even its brand--the product is the social network i.e., the network of users and the interactions between them. That's moat.

> If you think about it it's mostly the brand, not anything to do with taste. Same can be said about different beers or about Nike, Levi's, Apple (arguably) etc etc.

Brand is king in fashion (and to a lesser extent, low margin consumer products like cola or cereal) because fashion is largely about signaling status. I don't think this effect extrapolates to SO.