What Makes A Startup Successful?

You can skip the TechCrunch article and go right to the source: http://startupgenome.cc/

I went through the startup profiling and it was pretty accurate and quite worth it. At the end, it also gives some pretty useful advice on moving forward. Definitely recommend this if you're doing a startup.

High intensity, singular focus, product/market fit (http://pmarchive.com/guide_to_startups_part4), and determination (http://paulgraham.com/determination.html).

Good article. What would be an example of premature scaling in a startup? Too many hires?

You can scale prematurely in different trajectories: customer development, product development, hiring, etc.

An example could be hire a salesforce before having a paying customer or to hire middle management with less than 15 people. On the product side its for example spending lots of time on a scalable backend before even having the user and payer identified.