Is Justin Bieber's bizarre behavior a sign of something more?

Just three years ago, Justin Bieber, barely sixteen and flanked by a small personal posse demurely watched Liza Minnelli perform at Perez Hilton's 32nd birthday bash in Hollywood, nodding shyly and going almost unnoticed, with the exception of a few fans who sauntered over to commend the still emerging star on his recent successes.

But even then, autographs and photos were strictly "off limits" inside the bash as per his super-sized security guard, as the little boy-like singer hid behind his long bangs, eyes twinkling.

Now fast forward to 2013, and Bieber, 19, is the world's ultimate pop prince exhibiting an onslaught bad behavior and prompting questions of whether he has reached his peak.

"He has kind of appeared zonked out and strange for a while now," one source with ties to Bieber for several years now, told FOX411's Pop Tarts column. "And some who worked with him from the beginning are upset that he's abandoned his underground cred to pump more poppy selections like 'Beauty and the Beat.' He's talented, but right now he's a self-indulgent waste."

And given his latest "rough" patch – in Bieber’s words – the star has many industry insiders wondering if there is more to his wild ways than the ills of fame and fortune.

"Ahhh! Rough morning. Trying to feel better for this show tonight but let the paps get the best of me," Bieber tweeted last week, addressing an incident in which he was caught on camera hurling a string of expletives and threatening to "f***ing beat the f**k" out of a London paparazzo.

In addition to that little explosion, Bieber played four shows at London's O2 arena, igniting upset when he turned up to one show two hours late citing "technical issues." At a different performance, the "Baby" singer walked off stage mid-way to receive "oxygen and treatment" backstage.

The Biebs ended up in the hospital that night, which was all made oh-so-official when he tweeted out a (shirtless, naturally) photograph of himself in a hospital bed.

And New York-based publicist Elissa Buchter said his hospital visit reminded her of another young Hollywood troublemaker.

"When a star has to leave the stage after passing out, and ends up in hospital it is a clear indication that something is wrong. His recent 'health scare' is reminiscent of a young Lindsay Lohan who was constantly plagued by bouts of alleged 'exhaustion' early on," she said.

But Bieber apparently isn't too happy to be compared to LiLo. On Thursday, he ranted on Instagram about his rocky relationship with the press, taking a jab at Lohan.

In the sentence, now deleted from the post, Bieber wrote "to those comparing me to Lindsey [sic] Lohan look at her 2012 tax statements."

Bieber boasted in the rant that he has had five number one albums-- all before turning 20.

Still, like Lohan, Bieber has been getting press attention lately for all the wrong reasons. 

After a recent performance in Birmingham, Bieber returned to his London hotel in the early hours, braving the almost-freezing winter temperatures to stride from his car to his room sans a shirt.

That one even caught the attention of actress Olivia Wilde.

"Bieber, put your f***ing shirt on," she tweeted. "Unless you lost all your shirts in a fire in which case my condolences and please purchase a new shirt."

So what is really going on here? Is the Biebs dangerously unraveling before our eyes?

"Justin Bieber's toxic behavior is the result of too much too soon. Although he is in a very adult world, he has been granted unlimited access to anything he wants and is surrounded by ‘yes men’ who validate his behavior," Buchter said.

Los Angeles-based medical professional Dr. Damon Raskin called Bieber’s latest escapades nothing short of "bizarre."

"The passing out on-stage could be related to a lack of sleep, poor nutrition or dehydration," he observed. "And it could be a sign that he is getting burned out."

And while industry expert and founder of Betafish Music, Jed Smith, acknowledged that the fainting is an obvious warning signal that "something is amiss," he described Bieber's behavior as quite simply, "unremarkably brattish."

"It seems a waste to put as much effort into a concert schedule as he personally has, and tear it all down with a few tantrums," he said. "Because that 'brat' label he's working hard to achieve will stay in people's memories for a long time."

Lately the star has been photographed flashing gang signs, wearing a gas mask and even possibly smoking marijuana. Bieber attempts to gain street cred may be harming his credibility as a performer.

Some fans are clearly turned off by his new bad boy image.

The Canadian native was slated to perform back-to-back shows this week in Portugal but was forced to canceled the second show at the last minute. Multiple news outlets, including Agence France-Presse and TMZ, reported the cancelation was a result of an "insufficient demand" in ticket sales.

However, crisis management expert, Ronn Torossian, CEO of 5WPR, argued that Bieber is simply going through a typical teenage rebellion.

"Even though he is a mega-star, one shouldn’t forget that Justin Bieber is a 19-year old kid. Teenage boys all rebel in same shape or form," Torossian said.

But regardless of why Bieber is acting out, Smith said this period could have long-term ramifications on his standing as young Hollywood's biggest singing sensation.

"Now would be a great time for a moment of humility," Smith suggested. "Bieber could apologize to the fans he's blown off, allow some public insight into the pressures of world-class concert touring and being newly young and wealthy. If he doesn't turn perception of himself around eventually, he will be freak-showing his way on to a spot on ‘The Surreal Life.’"

A rep for Bieber did not respond to a request for comment.