Gladwell on Macintyre on Philby and the problem of trust

In Trust No One Malcolm Gladwell looks at Ben Macintyre’s book A Spy Among Friends: Kim Philby and the Great Betrayal:

“A Spy Among Friends: Kim Philby and the Great Betrayal” (Crown) is the latest in Ben Macintyre’s series on twentieth-century espionage (including the best-selling “Operation Mincemeat”). All are superb, and “A Spy Among Friends” is no exception. Macintyre gives the familiar story of Philby new life, putting the case in its full social context.

I found it especially interesting because in the middle of the article Gladwell talks about the damage caused by two very different security models: the high trust model and the trust no one model. The former is prone to false negative errors (traitors like Philby), the latter to false positives (Wright erroneously accusing a prime minister of treason). But which is worse? In the former case secrets are lost and lives destroyed (literally in the Philby case when betrayed agents were executed by the Soviets). In the second, organisations may become unworkable resulting in nothing being achieved. As the article asks:

What did more damage—Philby’s treachery or the subsequent obsession among spy officials with preventing future Philbys?

It did make me wonder if a country might be better off having no intelligence service at all.