It may be an unwritten rule, but I'm pretty sure it's a rule nonetheless. If you're going to make a movie called SEX TAPE about a suburban couple who make a three-hour-long sex tape to spice up their marriage, you have to have nudity for it to be both funny and effective. And when I say nudity, I mean committed baring of all parts from both leads, and not some Cameron Diaz ass double. Hire someone who is both funny and willing to commit to the conceit of the film. We know from films like FORGETTING SARAH MARSHALL that Jason Segel (playing Diaz's husband, Jay) is not against going full frontal for laughs. I'm not saying we needed prolonged actual sex acts on screen, but give us some amount of nudity to enhance to laughs, because putting it all out there can be very funny.
SEX TAPE actually does have one example of someone going the extra distance, although not in a naked way, and that person is Rob Lowe, who plays Hank, the mild-mannered CEO of a company looking to buy Annie's (Diaz) mommy blog. He has outlined a fairly conservative image he'd like Annie to project, and a leaked sex tape is not part of that image. When she and Jay end up at Hank's house, he has a prolonged conversation with Annie that gets stranger and more deranged with each passing second, and it's hilarious...while the rest of the movie struggles to generate consistent laughs.
The premise is fairly basic. Jay and Annie make the recording; Jay gives out a bunch of his company's used iPads as gifts, but said devices are still synched up to each other and the Cloud, so the video gets loaded onto a handful of gifted iPads, and the couple must race around to their friends to erase the video. A quick stop at their best friends Robby and Tess (Rob Corddry and Ellie Kemper) is kind of lame in the comedy department, because of course Robby is hesitant to give up the iPad when he finds out what's on it. The film only seems to really work when it's capable of surprising us, which isn't that often.
The film is especially disappointing because Segel, Diaz and director Jake Kasdan are capable of generating much bigger laughs, as they did in BAD TEACHER, which actually lived up to its title by presenting the worst possible character in Diaz. I know it sounds sexist to say, "Hey, show us Cameron Diaz naked, and I'll probably like the movie more." But that's only half true. I think showing Segel just as naked would have resulted in a better film as well. Instead we get a sexy romp that turns into a truly by-the-numbers film about marriages going sexually stale and the lengths people will go to rekindle the heat. Yawn.
A final-act trip to the offices of YouPorn (complete with an unexpected, but surprisingly dull cameo as someone playing the CEO of the porn site) is just a limp attempt to say a string of nasty porn site names in a row. Some of them are funny, but by this point in the film, it's too little too late. Part of the issue with the film might also be part of the reason any of it works. The screenplay is attributed to Kate Angelo (who I believe wrote the original version of this story) as well as the frequent writing team of Segel and Nicholas Stoller, who are quite proficient and talented comedy writers, whose names have never been attached to something quite this flat and uninspired.
SEX TAPE is neither especially funny nor sexy, and it's largely because the actors don't fully commit to the concept. You spend most of the movie noticing the lengths Segel and Diaz are going to not to show us their naughty bits, and the comedy suffers immensely because we simply stopped paying attention. Nudity in and of itself isn't necessarily funny, but as a tool in the hands of comedic actors of this caliber, it gives them something to work with. When you take it off the table, you're left with a whole lot of overplaying the parts in an uninspired story. I can't think of a worst formula for humor.