Jason Segel and Cameron Diaz in ":Sex Tape."

Jay (Jason Segel) and Annie (Cameron Diaz) in Columbia Pictures' "Sex Tape." (Claire Folger / Courtesy of Sony Pictures)

Judd Apatow didn't direct “Sex Tape” — it's startling to realize that he's only directed four features — nor did he produce it or (as far as can be determined) foster, doctor, or massage it. So why does it feel like a Judd Apatow film, albeit one with more raunch than he usually engages in? Maybe it's just that his network of collaborators all mine similar subjects, and “Judd Apatow” has just become a convenient way of categorizing a type of comedy currently in favor — Gen X (or maybe Gen Y) yuppie/slacker farces.

“Sex Tape” stars (and was co-written by) Jason Segel — a graduate of Apatow's “Knocked Up,” “This Is 40,” and “Freaks and Geeks,” and writer/star of “Forgetting Sarah Marshall” and “The Five-Year Engagement,” both of which Apatow produced. Maybe Apatow just stepped out for a few minutes to grab an orange/chocolate vente latte or something, and this project was pitched, written, shot and edited in his absence.

In any case, the result is about as slapdash as that fantasy would suggest. The problem is not the hook, which is a new twist on Ilf and Petrov's “The Twelve Chairs”: A couple, Jay (Segel) and Annie (Cameron Diaz) try to spice up their sex life by taping a one-take, three-hour version of Alex Comfort's classic book “The Joy of Sex”; the video accidentally leaks into “the cloud”; high jinks ensue as they try to find and destroy all the copies.

We learn in the opening that, during their courtship and the pre-offspring years of their marriage, Annie and Jay had an almost obsessive sex life, doing “it” every which way — except, thankfully, 99% of the ways the act can be observed on the Internet. The kinkiest they get involves risky locations, only slightly hidden from public observation. That variation is a second cousin of their dilemma in “Sex Tape,” though the connection is never discussed.

The contrivance by which the plot explains how it leaked without instantly spreading everywhere is: Jay is an L.A. music industry guy, whose workplace gives him a fresh iPad every time a new model is released. Jay in turn passes the old ones on to friends and acquaintances (including the mailman), and keeps them all synced so the recipients are up to date on his mixes.

Unfortunately, shortly before he and Annie make the titular video, he has upgraded from an app called FrankenSync to the new, more powerful Bride of FrankenSync, and, before he has the time (or perhaps the motivation) to erase the revealing video, it has been sent to the half a dozen people who have his old iPads. What's more, he receives an anonymous text about it, triggering the frantic search to retrieve the machines.

It's relatively easy for Annie to repossess Mom's, but she's also passed one on to strangely creepy toy company exec Hank (Rob Lowe), who is about to offer her big bucks to pick up “Who's Yo Mommy” — her blog about balancing marriage and child-rearing and work — which in her case is writing the blog. And Hank is very concerned about his company's image.

While they're in the midst of this, the video is sent to — but not yet posted to — YouPorn (which is real). For a porn site, the film must have been a product placement dream, even though the movie is mostly a pitch for Apple. The filmmakers do take one dig at Siri, which may be the funniest joke in the whole affair. (One wonders whether they had Android/Google on hold, in case the Apple deal fell through.)

There are perhaps half a dozen chuckles to be had in 95 minutes. The leads are likable, even as they screech at each other about their predicament, though it's sometimes hard to buy their technological naivete. The pace is nonstop frenetic, which begins to wear. Things pick up briefly in the third act, when an unbilled Jack Black shows up in a perfect bit of casting. But the film seems to think it's much funnier than it actually is. This is never more apparent than in the final montage of sex acts, as Annie and Jay watch the whole thing once before destroying it forever. The montage is only a couple minutes long, but it feels like it just goes on and on. It manages to make Diaz romping in various states of undress boring — no mean feat.

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ANDY KLEIN is the film critic for Marquee. He can also be heard on "FilmWeek" on KPCC-FM (89.3).