Groupon looked like a very high valuation, but any investment in a great company at any stage is almost always a good investment.

In my experience as CEO, I found that the most important decisions tested my courage far more than my intelligence.

As a company grows, communication becomes its biggest challenge.

How do you make your company a good place to work in general? That's a really really really large and complex set of skills. A lot of it is on the job training, combined with excellent mentorship.

The right thing to do is to thank them for their work, let people know that they're moving on, and ... you don't really have to explain all their personal details. It's more important to leave them with their dignity... and let them go on to live another day. Remember, what you say at that meeting, that's their reputation.

Note to self: It’s a good idea to ask, “What am I not doing?

I don’t believe in statistics. I believe in calculus.