The recent achievements from combining horizontal drilling with hydraulic fracturing are indeed impressive and have brought much-needed new volumes of liquid fuels to the thirsty U.S., which has long been the world's largest oil importer. (Shale gas is likewise an impressive accomplishment, but the U.S. was still a net gas importer in 2012, according to EIA data.) But these are not new technologies. The first horizontal well was drilled in the 1930s, and hydraulic fracturing was introduced in the 1940s. Both technologies have been thoroughly applied and refined at scale in real-world circumstances for many decades, with substantial federal support for research and development.
Methane hydrate extraction, which is still in the early stages of testing and requires techniques that have only recently been attempted for the first time, is in no way comparable to tight oil and shale gas extraction. Methane hydrates are not "being developed in much the same methodical way that shale gas was developed before it," and skepticism on methane hydrates isn't comparable to skepticism on shale gas. Skepticism isn't some fungible property of everything; facts about prices and production rates are essential.
Perhaps this is the real point of Mann's take on these new technologies: He confesses that he does not want to "miss the boat" on methane hydrates as he did on shale gas. That's a gambler's mentality, not a shrewd investor's.
Perhaps that is also why Mann chooses to perceive tight oil and methane hydrates through the lens of the peak oil debate, which occupies much of Mann's 11,000-word exposition on the history of oil and gas production. His he-said, she-said treatment of the subject, attempting to portray it as a simple matter of differing opinions between "Hubbertians" and "McKelveyans," gave far more credence to longtime and ardent peak oil critics like Verleger and Lynch, while characterizing the views of Campbell, Laherrère, and the "anti-fossil-fuel think tank" Post Carbon Institute as "not widely shared."
If he had any real familiarity with their work, Mann would know that the latter group recognize the importance of fossil fuels while being deeply concerned about their future. He would also know that many other analysts and petroleum scientists have done serious and highly transparent research on the subject of peak oil, including Jeremy Leggett, a petroleum geologist and former faculty member of the Royal School of Mines in London; Olivier Rech, who was responsible for IEA's petroleum forecasts from 2006 to 2009; dozens of independent analysts, petroleum engineers and economists who publish at The Oil Drum; and petroleum scientists like Kjell Aleklett of Uppsala University, and Chris Skrebowski, a former long-term planner for BP and senior analyst for the Saudi Oil Ministry.