Ask HN: Which startups are doing 'real' work?

Nowadays, millions of startups seem to starting all over the world and I am really doubtful whether they are sustainable in the long term. Most of them are probably going to make money for their founders when they sell it to some foolish large company, but I don't think they will add any value to the world in the medium or long term.

In fact, I can probably categorize them into the following - 1. Allows you to share something in Facebook or Twitter or through a similar platform 2. Has something 'social' with good marketing 3. Uses Lisp or similar, like Clojure, and people automatically assume it is great 4. Some foolish app with a million downloads which people will forget after a few months

Examples - utterly nonsensical startups like Pollground and LikeBetter. In fact, many of the YCombinator funded startups are similar in nature. This question was inspired by the article 'Eight Y-Combinator Companies to Watch'.

So which startups are trying to solve really tough problems, or working on something really revolutionary which actually requires knowledge of how computers work and not just provide a platform for people to be 'social'?

Example companies or projects (not necessarily new) I am talking about - SoundHound, RethinkDB (I have always been a fan of defmacro.org), ReiserFS, Apple, Microsoft?