Last October, T-Mobile made an astonishing announcement: from now on, when you travel internationally with a T-Mobile phone, you get free unlimited text messages and Internet use. Phone calls to any country are 20 cents a minute.

T-Mobile's plan changes everything. It ends the age of putting your phone in airplane mode overseas, terrified by tales of $6,000 overage charges. I figured my readers would be jubilant. But a surprising number had a very different reaction. “Why should I believe them?” they wrote. “Cell carriers have lied to us for years.”

That's not the first time that promises from a tech company have been greeted not with joy but with skepticism. When Apple introduced a fingerprint scanner into the Home button of the iPhone 5S, you might have expected the public's reaction to be, “Wow, that's much faster than having to type in a password 50 times a day!” But instead a common reaction was: “Oh, great. So now Apple can give my fingerprints to the NSA.”

Really? That's your reaction to the first cell phone with a finger scanner that actually works?

And it's not so unreasonable.

Technology used to be admired in America. We marveled at the first radio, the laptop computer, the flat TV. Tech companies were our blue-chip companies. An IBM man was a good catch—respected, impressive. We were proud of our technological prowess and of the companies that were at the forefront.

Today it's not so simple. Our tech companies have a trust problem.

Over the years they've brought it on themselves. Google tested privacy tolerance when it introduced Gmail—with ads relating to the content of your messages. (It doesn't seem to matter that software algorithms, not people, scan your mail.)

Then a team of researchers discovered that when you synced your iPhone, your computer downloaded a log of your geographical movements, in a form accessible with simple commands. (Apple quickly revised its software.) When Barnes & Noble understated the weight of its Nook e-reader in 2010 or overstated the resolution of the Nook in 2011, suddenly even product specs could no longer be trusted.

Next came news about the National Security Agency and its collection of e-mail correspondence, chat transcripts and other data from Microsoft, Google, Facebook, Apple and others. Those companies admit to complying with the occasional warrant for individuals' data, but they strenuously deny providing the nsa with bigger sets of data. Do you think that makes the news any easier to take?

Of course not. We're human. We look for patterns. Each new headline further shakes our trust in the whole system.

These days tech companies make efforts to respect, or at least to humor, the public's alarm. In the latest iPhone software, for example, Apple has provided an almost hilariously complete set of on/off switches, one for every app that might want access to your location information.

But it may be too late for that. These companies' products are impossibly complex. There's no way for an individual to verify that software does exactly what we think it does. How do we know those iOS 7 switches do anything at all?

Every time a company slips up, we can only assume that it is just the tip of the iceberg. It may take years for these companies to regain our trust.

But this “I don't trust them anymore” thing sounds distinctly familiar. And it isn't specific to tech companies. At one time or another, haven't we also learned not to trust our government? Our police? Our hospitals? Our newspapers? Our medicines? And, goodness knows, our phone companies?

It's too bad. Mistrust means a life of wariness. It means constant psychic energy, insecurity, less happiness. And then, when we finally get what should be terrific news from a tech company, we're deprived of that little burst of unalloyed pleasure.