Wrong Reasons for Getting a PhD

From Deaniel Lemier's blog:

• I’m building a business as a consultant and a Ph.D. sounds cool. Do not even think about a Ph.D. for this reason. Consultants with a Ph.D. do not, in my experience, earn more money.
• I already have a job and my current project would make a great Ph.D. thesis. You think so? Very few industrial projects make a good Ph.D. thesis. In fact, it is extremely hard to reconcile industrial interests with Ph.D. work.
• I would earn more money if I had a Ph.D.: this is false. Earning a Ph.D. means you are using up a lot of your time to make an entry into the academic world. Financially, it might not be a complete disaster, but it is hardly wise.
• I want to impress my friends. A Ph.D. might impress your friends, but so would earning 1 million dollars by the time you are thirty, or becoming a top lawyer or saving lives in a hospital. Consider that many people who go for the Ph.D. have to go live in cities they wouldn’t have otherwise chosen. There are many ways to impress your friends, but a Ph.D. is probably the worst option.
• I’m so smart, it is my destiny. Actually, really smart people choose easier paths. If you are down to the Ph.D. path, well, something is a bit wrong with you to begin with. But that’s ok, there are many of us.