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Most people use social media sites to keep in touch with old friends and to make new ones. But more and more, law enforcement agencies are using them to fight crime – and some criminals are making that task very easy.

Take Chris Crego, a fugitive on the run from police in New York. Police who arrested him in Indiana say he all but turned himself in by posting his workplace on his MySpace and Facebook pages.

Take Robert Powell, a Florida man convicted of murdering of his friend Joseph Duprey. He posted pictures of Duprey on his MySpace page next to the words "rest in peace" and "live through me" -- hours before Duprey's death was even reported to police.

And it's hard to forget Jonathan G. Parker, a 19-year-old from Pennsylvania who was arrested and charged with burglary after a woman found her home ransacked and her jewelry stolen. Police say the woman found something else, too -- Parker's Facebook account open on her home computer.

Click here for more suspects caught web-handed.

The trend has authorities often skipping the squad cars for the keyboards in hopes of finding leads in investigations.

"People all the time brag about their exploits. You'd be surprise how many cases have been solved throughout the nation…where they've mentioned how they've successfully solved a crime using information retrieved off of a Web site," Jack Rinchich, President of the National Association of Chiefs of Police, told FoxNews.com.

Rinchich of West Virginia says police around the country are finding success using social media as an investigative tool --even if they don't find a smoking gun.

"Sometimes it [the information] may not be incriminating enough to affect an arrest, but it supplies enough information from an investigator's standpoint that it points them in the right direction in terms of solving the crime or researching the crime," Rinchich said. "It can be a valuable tool in solving and preventing crime."

Michael Fertik, CEO and founder of ReputationDefender.org and an adviser to the FBI, says he hears stories like these from agents all the time.

"Basically they tell me that they sit on the Internet all day and look for information on suspects and potential suspects," Fertik told FoxNews.com.

FBI agents are even creating fake Internet identities to deceive suspected criminals into befriending them online in hopes that they'll disclose incriminating information, a new Justice Department document obtained by the legal advocacy group Electronic Frontier Foundation shows.

According to the document, agents scan suspects' profiles for helpful information such as location, potential motive to commit a crime, and photographs containing guns, stolen goods or any other evidence of criminal behavior. If they can't get to the suspect's profile, sometimes getting to their list of friends is enough.

Seattle bank fraud fugitive Maxi Sopo had a private Facebook page, but detectives found him anyway after he posted messages boasting about his new life in Mexico. Unfortunately for Sopo, one of his Facebook friends just happened to be a former Justice Department employee, who turned him in.

Fertik says social media have aided crime-fighting in the private sector, as well.

"Not only are law enforcement using it, not only can you count on law enforcement using it, not only are law enforcement delighted that these pieces of information, these bread crumbs, are being left everywhere, but also people can do it yourself now," he said. "People can use technologies to either make themselves vulnerable or help find the thief who's trying to do them harm."

Police say that's exactly what happened in the case of Daniel Gill, an Oregon man arrested on burglary charges after he allegedly tried to sell the equipment he stole from an Oregon extermination company on Craigslist.

"In this case it was one of the business owners that went on Craigslist and was shopping around to see if she could find her property on Craigslist, and lo and behold she found it," Linn County Sheriff Tim Mueller told FoxNews.com.

Mueller says the owner's discovery enabled detectives to obtain a search warrant to search Gill's house, where they found even more than what they were looking for.

"We found all kinds of good stuff there out there -- that he'd been stealing not only from that neighbor but other neighbors as well!" he said.

Fertik calls cases like these the start of a "do-it-yourself movement" in busting criminals.

Pat Brosnan, a retired NYPD detective and the founder of the private security firm the Brosnan Group, agrees.

"We utilize data posted on blogs and various social networking sites like Facebook, MySpace and Twitter to validate and corroborate information we have developed regarding the target of an investigation," Brosnan told FoxNews.com. "…These sites are a potential treasure trove."

But Rinchich says people still have to remember not only to be careful about what they put on the Internet, but also about what they do with the information they find there.

"I wouldn't necessarily want to take it on the face of it as prime evidence, because sometimes people say things and they're boastful and they didn't really do it, they're just showboating for their friends," he said. "So you have to be really cautious… because you might get the wrong person."

Still, Rinchich says, if people are "dumb enough" to leave a criminal trail to their wrongdoings on the Internet, he's happy to pick up the pieces.

"If there's any technological resource that would benefit law enforcement, as long as it's legally achieved, I say go for it, utilize whatever resources necessary, to prevent and to solve crime."