Warren doesn't put any "stock" into investing in new industries since 1) investors will run up share prices in anticipation of immediate wealth, 2) there is lots of competition in new industries, 3) many of the new companies don't survive and 4) the new businesses don't have a history of a product with a durable competitive advantage.
A great example of Warren passing over a new and in fashion industry was during the .com internet boom. It was during this time that Warren was referred to as a "dinosaur investor" since he wasn't investing in technology stocks, but rather was investing in "old stodgy"companies.
Warren believes that investors should ask themselves the following question before making an investment decision: if I could buy a company outright at the current market price, would I do so with all my cash? If the answer is yes, then he suggests you should invest in the company, even if it means only acquiring a modest amount of shares. Conversely, if an investor had the financial means but is not willing to purchase the company outright, he feels that you shouldn't even buy a single share in the company.