It's worth remembering that Dale Carnegie was a salesperson. Salespeople can afford not to criticize. That's because, when the sales negotiation ends, they will

It's worth remembering that Dale Carnegie was a salesperson. Salespeople can afford not to criticize. That's because, when the sales negotiation ends, they will present you with a contract to sign -- a contract that has been written by some of the bluntest, most critical, most paranoid people on Earth: Lawyers. Salespeople get away without criticizing because they outsource the task to lawyers. As an engineer, it pays to have great sales skills, but you have a much harder task than the average salesperson, because ultimately your job is more like the lawyer's. Your raison d'etre is to build things that actually work. In the famous words of Richard Feynman: For a successful technology, reality must take precedence over public relations, for nature cannot be fooled. And that forces engineers to be critical. The decisions they make in the early parts of a project could make an order-of-magnitude difference in the eventual cost. If they don't find the holes in the plan ("gosh, won't your proposed friends-of-friends search scale as O(N^3) and ultimately bring your social network to its knees?") or properly evaluate the likelihood of rare-but-deadly scenarios ("is it worth a million dollars to guard against the odds that our offsite backup's drive controller will fail just as an earthquake takes out our primary data center, or shall we just buy insurance?") the whole enterprise could fail catastrophically. Perhaps many engineers err on the side of too little Dale Carnegie. But it's telling that many of the great ones don't so much avoid criticism as get really, really good at selling criticism to you. Think of Steve Jobs, one of the most critical people in human history, who gets away with it by playing the role of a fanatically driven artist. Or Torvalds, who is really blunt but turns it into a joke: He makes fun of his own bluntness (he named his DVCS "git" -- look it up in the dictionary!), he's deliberately over the top, and he plays strictly to an audience of engineers, who are more likely to see the humor in lines like "CVS users are ugly and stupid" than the average person is. Try to moderate your criticism, but don't forget that ultimately it is your job. Don't lose focus on it.