This post is a bit more than a year old, but I just came across it this morning. Paul Graham uses a variety of threads to explore the concept of what makes a good startup.

The very best startup ideas tend to have three things in common: they’re something the founders themselves want, that they themselves can build, and that few others realize are worth doing. Microsoft, Apple, Yahoo, Google, and Facebook all began this way.

Why is it so important to work on a problem you have? Among other things, it ensures the problem really exists. It sounds obvious to say you should only work on problems that exist. And yet by far the most common mistake startups make is to solve problems no one has.

A thoughtful read that rings true for me.