David Beckham, J.K. Rowling and Sir Richard Branson have all lent their names to her cause. Her face has appeared on the cover of People magazine and Friday her parents released 50 balloons bearing her picture -- one for each day she's been missing. All the attention has not yet led authorities to 4-year-old British girl Madeleine McCann, but multiple tips and possible sightings on the Mediterranean island of Malta have brought new hope to the search. Though experts in kidnapping warn that high-profile cases generate more false leads.

Detectives in Malta have been investigating more than a dozen reported sightings of Madeleine in the last month.

Madeleine was allegedly abducted from her hotel room while vacationing with her parents in Portugal. Her parents, Gerry and Kate, say they left her alone with her 2-year-old brother while they went to dinner just 100 yards away. When they went to check on the children, the door was open and Madeleine was gone.

The case spurred a flurry of media attention, and Madeleine's parents worked hard to keep that attention from flagging as time dragged on. Videos appealing for help in the search were broadcast at soccer games in Europe and millions of dollars have been offered as a reward for her safe return.

Ernie Allen, president of the Center for Missing and Exploited Children, said this case has created a "two-edged sword." On the one hand, the attention has kept people looking for Madeleine, but on the other hand so much attention can create an excessive number of false sightings.

Even so, Allen said it's a good thing that people are filing reports. "Clearly law enforcement is following up on these leads in an aggressive way," he said.

Madeleine's parents continue to hold onto hope that their daughter will be found alive. Missing children are most likely to be found in the first few minutes and hours after their abduction, but Allen said the 50-day mark should not be seen as ominous.

"There is a very high degree of likelihood that she can and will be found and that even though it's been 50 days, the prospects for finding her alive are significant," said Allen. "It's important that people not assume that since she's been missing for 50 days that we're looking for a body."

Earlier this year, two kidnapped boys in Missouri were recovered. Ben Ownby, who had been missing for five days, was found with another missing child, Shawn Hornbeck, who had been missing for four years. Elizabeth Smart was missing for nine months when she was found in Utah.

Allen said he tells parents of missing children that the most important thing is "to keep hope alive, because the world tends to forget."

Online: The National Center for Missing & Exploited Children The National Center for Missing & Exploited Children