They are the Hard to Buy For, and like the devil himself, they assume many forms: the hobby-less brother-in-law; the enthusiast so serious about her leisure-time pursuits that an outsider could never get a gift right; the dad who overnights himself whatever he wants; the teenager with unknowable preferences; the mom who insists she needs nothing; the baby with fussy parents.

Americans are planning to spend $586.1 billion this holiday season, up 4.1 percent from last year, according to the National Retail Federation. What those statistics don’t show is the amount spent on gifts that present a challenge so frustrating, or that become such a time drain, that the gifter starts to develop a small irritation, or a full-blown hostility, toward the giftee.

The stress of satisfying the Hard to Buy For is probably worse than ever this year, as a combination of factors — the still-lousy economy, the growing recognition that all this extra stuff we buy harms the earth, and the fact that it doesn’t leave us happier — makes wasteful spending feel worse than ever.

And yet, the gifts must go on.

In Brookline, Lindsay Durr’s boyfriend is going on his fifth year of angst. “I’ve learned over the years that it cannot be something practical,” said the long-suffering, long-shopping beau, Brendan Dougherty, 27, an accountant. “That means it has to be a luxury item, and since it’s a luxury item, there’s often an element of style that’s involved.”

Here’s where things go downhill: “She has a very unique style,” Dougherty said of his beloved Durr, a publicist. “I feel it walks a fine line between very eclectic and out there, and being kind of ugly. It’s tough to tell whether something would fit into her style of not.”

After one too many failures — starting with a Marc by Marc Jacobs bag that was too similar to one she already owned — Dougherty has switched tactics. One year he took refuge in the “experience” gift and the couple went to Ogunquit, Maine. Sometimes he goes the “just being together is gift enough” route, a sentiment that Durr, 26, calls lovely. “But,” she added, “sometimes you just really want a handbag.”

Pam Boyden, 45, a financial analyst from Charlestown, also finds the best defense is a good offense. “You get what you get,” is how she summed up her attitude toward the Hard to Buy For. And if you don’t like it, she added — addressing an imaginary ingrate, as she shopped at Marshalls, in Fenway — “you can go back to the store and stand in line and return it.”

Never mind that the world’s bounty is a mere credit card swipe away, anyone with a member of the HTBF on his or her list has experienced the helplessness that sets in before the shopping even starts. “It’s stressful,” said Kim Quinn, a nurse practitioner with a mother who’s Hard to Buy For. “You have to give a gift — it’s taboo not to. But you don’t want to waste your money on something they don’t need or want.”

With shopping stress escalating, the Globe asked Kit Yarrow, a consumer psychologist from Golden Gate University, in San Francisco, to profile these most-dreaded recipients.

“Pretty much all men,” she began. “They want really big things. They don’t want a little hinky iPod. They want a sports car, or some major electronics.”

Enthusiasts — generally male, she noted — also present a challenge. “I just finished interviewing 42 people on bad gifts they’d gotten,” Yarrow said. “One guy said his mom gets him Boston Red Sox trinkets that are cheap and tacky. A golfer was aghast that someone was trying to buy him golf equipment. Or we know they love fishing, but buying them anything is a recipe for failure. So we hate them for that.”

Hmm. Maybe neither giving nor receiving is good.

The third group, Yarrow said, may be even tougher to satisfy than the enthusiasts. “They are so exacting and knowledgeable that they tend to be extremely particular. The idea that you’d pick something out for them puts fear into your heart.”

Not to make excuses for the Hard to Buy For, but there’s a reason people are so picky. We already have too much stuff. In fact, recent research by UCLA-affiliated social scientists found that Americans’ plethora of possessions is making families feel overwhelmed by clutter.