Hollywood's summer blockbuster season has begun, and with it a flurry of celebrity romances.

Katie Holmes (search), whose new movie, "Batman Begins," (search) comes out on Wednesday, has been just about everywhere lately touting her love for "War of the Worlds" (search) star Tom Cruise (search), and vice versa.

And Brad Pitt (search) and Angelina Jolie (search), who co-starred in last weekend's box-office hit "Mr. and Mrs. Smith," (search) still have not revealed whether or not they're in a relationship, but the rumors are hot, hot, hot.

To the conspiratorial sort, the concurrence of these relationships and their respective movie releases is more than a coincidence. Many Americans are wondering: How many of these celebrity romances are real — and how many are elaborate public-relations stunts?

"Whether or not you've got the notion that the PR handlers are twisting their moustaches, deciding 'You and she should have a relationship together,' there certainly have been concocted romances before," said Robert Thompson, professor of popular culture at Syracuse University.

"A good portion of the stars in the golden age of Hollywood," he pointed out, "had their biographies created from whole cloth by their press agents."

Without question, the romance raising the most eyebrows is the entity now known as "TomKat."

Cruise, 42, an aging idol who can no longer guarantee box-office gold, has the alien-invasion movie "War of the Worlds" coming out June 29.

The 26-year-old Holmes, who hasn't yet turned her starring role on "Dawson's Creek" into silver-screen success, has "Batman Begins" opening only two weeks earlier.

For Cruise, dating an up-and-coming actress could reacquaint the "Top Gun" and "Risky Business" star with a younger audience.

And on that first date with Cruise, something in the back of Holmes' mind may have whispered that the last two women he is known to have romanced, ex-wife Nicole Kidman (search) and "Vanilla Sky" co-star Penelope Cruz (search), were both also up-and-coming stars in the U.S. when he started dating them — and mega-stars by the time both relationships ended.

Also noteworthy: Cruz and Cruise first stepped out together around the time of the "Vanilla Sky" premiere, and Kidman and Cruise started dating during the making of "Days of Thunder."

Moreover, Cruise, Kidman, Cruz and Holmes are all represented by Tinseltown powerhouse Creative Artists Agency.

"OK, it's pretty easy to see why people are wondering," Parade magazine entertainment writer Robert Moritz said. "There's well-timed publicity, and I don't even think anyone knew [Holmes] was going to be in 'Batman Begins' until the news that they were dating came out. If you saw these two people in a room, you wouldn't pair them up."

Toss in the unusual way the famously private Cruise's publicists have been touting the relationship, sprinkle with the just-won't-die rumor that Cruise is gay and top with a much-dissected couch-jump on "Oprah," not to mention the buzz that Cruise "auditioned" several other young actresses to be his new girlfriend before settling on Holmes — and you've got an official conspiracy theory.

"The real way you tend to hear about a celebrity relationship is [when] the publicists issue formal denials," Moritz said. "But in this case, there was a press release released on the wire before anyone even thought this was in the realm of possibility."

"Here's a guy who was one of the most famous faces, yet extremely private," Moritz added, "and now he's giving Jen Schefft from 'The Bachelorette' a run for her money with public displays of affection."

Whether it's fact or fiction, the Cruise-Holmes romance may have started a backlash, one not helped out by Cruise's recent pro-Scientology, anti-psychiatry rants — or by Holmes' even more recent disclosure that she is converting to the controversial religion.

"[Staging a romance to promote a film] has not necessarily been a successful technique in the past," Radar magazine associate editor Danielle Stein said. "It doesn't mean people will go see a movie, and I think a lot of people would have gone to see Katie's movie anyway."

Almost as talked-about is the relationship — romantic or not — between Pitt and Jolie, who happen to be in the currently playing "Mr. and Mrs. Smith."

Most recently, the pair has refused to confirm or deny a love affair — much as Cameron Diaz and Justin Timberlake's publicists once swore up and down that they weren't dating either (and now the boy-band superstar and "Charlie's Angels" blonde are joined at the hip.)

At the same time, though, savvy PR people know that refusing to talk breeds more speculation.

Few entertainment journalists, however, think that the Pitt-Jolie romance is being faked.

"You'd have to give a Nobel Prize to Jennifer Aniston (search) if it's a public-relations ruse," Moritz said. "There's no evidence they've been looking for public attention. Plus breaking up a marriage for good PR? No way."

Stein said the chemistry that Pitt and Jolie exude when they're together leads her to believe that there's a real romance there.

"I don't think this is a concocted relationship, and I think that's what the difference is with Tom Cruise and Katie Holmes," she said. "I think that the public can see through a relationship concocted just for publicity."

Intentionally or not, the alleged "Brangelina" liaison helped drive people to see their movie. "Mr. and Mrs. Smith" scored $51 million and a spot at the top of the box office last weekend, despite tepid reviews.

Pitt and Jolie are also both repped by CAA.

Conspiracy theorists also hold up examples of much-promoted Hollywood romances that turned out to be hype, such as Natalie Portman (search) and Hayden Christensen (search) when "Star Wars: Episode II — Attack of the Clones" came out, and Kevin Spacey (search) and Helen Hunt (search) when "Pay It Forward" hit theaters.

Others point to the unlikely couples who have, in the end, proven to be genuine: Timberlake and Diaz, Demi Moore (search) and Ashton Kutcher (search) and Antonio Banderas and Melanie Griffith.

In fact, it's all too natural for stars to hook up on the set, according to relationship expert April Masini of AskApril.com.

"If anything, they're the victims of movies," she said. "Pity them for having been reeled in by the seduction of Hollywood. [They're] both there working toward a common goal, the hours are long and intense, and if there's someone attractive nearby, it's human nature."

Opponents of the conspiracy theories also point out that in an age when gossip hounds document almost every aspect of stars' private lives, maintaining an illusion of a Hollywood romance is harder than ever before.

"How could anybody keep a secret in Hollywood?" Moritz said. "We live in this age where paparazzi are getting so much money for a picture of people spilling lattes on their blouses, and in a town with so many big mouths, it boggles my mind that no one comes out and says, 'Here's the proof that this is fake.'"

And finally, there's the romantic take.

"I don't want to jinx love," said CosmoGIRL entertainment editor Jessica Blatt. "At the end of the day, you just don't know. And instead of being cynical, just remember that you just don't know.

"If it is love, all the best to them, I'm happy for them. Let's just see what happens to their relationship by the time their movies are out on DVD."