Productivity comes from interactivity and the exchange of ideas and talents.
People are happiest when they're encouraged and trusted.
An airport functions far better when we don't strip search passengers. Tiffany's may post guards at the door, but the salespeople are happy to let you hold priceless jewels. Art museums let you stand close enough to paintings to see them. Restaurants don't charge you until after you eat.
Compare this environment of trust with the world that Paypal has to live in. Every day, thousands of mobsters in various parts of the world sit down intent on scamming the company out of millions of dollars. If the site makes one mistake, permits just one security hole to linger, they're going to be taken for a fortune. As a result, the company isn't just paranoid–they know that people really are out to get them.
This is the fork in the road that just about all of us face, whether as individuals or organizations. We have to make an assumption about whether people are going to steal our ideas, break their promises, void their contracts and steal from us, or perhaps, that people are basically honest, trustworthy and generous. It's very hard to have both postures simultaneously. I have no idea how those pistol-packing guys in the movies ever get a good night's sleep.
In just about every industry (except electronic money transfer, apparently), assuming goodwill is not only more productive, it's also likely to be an accurate forecast.