The next time you plunk down $500 to rent a Porsche for your best friend’s birthday, drive it through the winding hills near Malibu and snap photos, be careful what you do with the pictures after. They could go viral.

This very thing happened recently to Jon Wienner, a young New York deejay whose photo of a buddy and his rented Porsche ended up on Rich Kids of Instagram.

(Jon Wienner/Wienner’s photo appears on Rich Kids of Instagram with the caption: “Best birthday present ever. Best friend ever @djtheory #sundayfunday by evan pow.)

The controversial new Tumblr is a collection of snapshots from the photo-sharing site that depicts the children of wealth and privilege — summering in the Hamptons, lounging on yachts and posing by their luxury cars.

One does a back-flip out of a helicopter near St. Tropez. Others snap pictures of their restaurant bills — allegedly paying thousands of dollars for lobster, champagne and high-end liquor.

In the warm patina of the Instagram, the youngsters appear to be living over-the-top lifestyles — and enjoying every moment.

“Our everyday is better than your best day,” reads one caption, a bit tauntingly. And, “Do you have a horse in your backyard? Didn’t think so.”

The Tumblr long ago went viral, but the public hand-wringing goes on. Just what does it say about our culture that it so glamorizes excess?

“Preteens posing with helicopters they did nothing to earn. . .provides an easy in for commentary on the state of the American dream. (Dead.),” Rebecca Greenfield wrote for the Atlantic Wire.

Yet: “People are obsessed with it,” says Wienner, 22. Out of nowhere, it seemed, came a peek into a private world that few knew existed, with kids who “only flew private” and “did back flips out of helicopters.”

Wienner grew up in Connecticut in relatively modest means, but has rubbed elbows with the super-rich at prep school and at DJ gigs in New York and L.A.

He said the Tumblr first featured pictures of his friends, a relatively close-knit group of young teens and twentysomethings of famous parents in Los Angeles, such as Barron Hilton, Paris’s little bro. He was shown walking on the beach arm-and-arm with a comely, bikini-clad blonde.

Wienner says he understands the blog’s somewhat “douche-y” appeal, although he says it has gone downhill since its debut in early July. Now, anybody can contribute.

He admits that the “funniest thing” about ending up on the bratty blog was that the photo caption on his picture— “Best birthday present ever” —leads people to believe he actually bought his friend Evan Powell, a Los Angeles art rep, the luxury sports car for his birthday, rather than just renting it for the day. They both ended up being the “Porsche kids on the ‘Rich Kids of Instagram,’ ” he says.

“Before it was a chronicle of the children of the one percent,” Wienner says. “Now anybody can post a photo of his big bottle of Dom [Perignon].”

The creator of the Tumblr said via email that he (or she?) preferred to remain anonymous.

“A few misspelled Instagram searches led to the uncovering of opulence, so we put it on Tumblr,” the creator explains. The widespread response has been “entertaining,” and the most popular picture so far has been of a gold-plated AK-47.

About that gun. . .

The AK can be yours for a mere $9,000, according to Jake Lifson, the manager of Blue & Cream boutique in East Hampton. It used to be a functioning weapon until it was de-armed and gilded. Now, he says, it’s a work of art.

A gold-plated AK-47, appearing on the blog "Rich Kids of Instagram." (Blue & Cream Boutique)