Have you become a victim of an internet scam or fraud? Should you report it? The answer is yes. There are organizations out there that want to help you. Just because a crime is perpetrated via the net doesn't make it any less of a crime.
Let's look at some resources you can use to report internet-based crimes and fraud.
The Internet Crime Complaint Center is a partnership between the US Federal Bureau of Investigations and the National White Collar Crime Center. The ICCC is a good place to report more serious crimes involving: online extortion, identity theft, Computer Intrusion (hacking), Economic Espionage (Theft of Trade Secrets), and other major cyber crimes. If you don't feel the crime committed against you falls into these categories, but you still feel the crime is serious enough to report, then you can still report it to the ICCC. If it doesn't fall under one of their categories, they might be able to direct you to an agency that does handles it.
The Online Better Business Bureau of the US and Canada has a site for consumers that will aid you in making complaints against internet-based retailers and other businesses. You can also search their database to see if a merchant has other complaints against them and whether they have been resolved or not.
The USA.gov's Internet Fraud Information page is a jumping off point for the reporting of crimes including phishing attacks, Internet investment fraud, consumer complains regarding internet marketing, scam e-mails, and much more. The site will link you to the appropriate agency's who handles crime reporting for each specific type of crime.
The eBay Security Center: General Marketplace Safety site can assist you with reporting auction related fraud / and scams to the proper authorities and also provides a way for law enforcement to find out if someone is trying to auction merchandise stolen from you if you have been the victim of a property theft.
The Facebook's Security site will allow you to report account hacks, fraud, spam, scams, rogue applications and other facebook-borne threats.