Consumers filed more than 1.8 million complaints with the Federal Trade Commission last year. And for the 12th year in a row, identity theft accounted for the biggest slice of the complaint pie.

According to the FTC, it received 279,156 complaints related to ID theft in 2011. That made up a whopping 15% of all gripes filed with the commission.

On a somewhat positive note, it marks the second year in a row that the percentage of ID theft complaints has dropped. In 2009, this category represented a full 20% of complaints filed. Of course, there were only 1.4 million total complaints that year, so the actual number remains virtually unchanged.

Also making the list for most-complained-about topics:
Debt Collection: 180,928 (10%)
Prizes, Sweepstakes, and Lotteries: 100,208 (6%)
Shop-at-Home and Catalog Sales: 98,306 (5%)
Banks and Lenders: 89,341 (5%)
Internet Services: 81,805 (5%)
Auto Related Complaints: 77,435 (4%)

These numbers are all tracked by the FTC’s Consumer Sentinel Network, a database available to more than 2,000 civil and criminal law enforcement agencies in the United States and abroad. These agencies can use the Network to research cases, track targets, and identify victims.

Additionally, agencies at the federal and state level — along with a small group of participating private-sector organizations like the Better Business Bureau, can contribute complaints to the Sentinel database.

“The Consumer Sentinel Network is a treasure trove of information for law enforcers,” said Richard Cordray, Director of the Consumer Financial Protection Bureau. “We plan to contribute consumer complaints we receive at the CFPB to the Network and urge other state and local law enforcers to join the Network, too.”

You can check out the whole 105-page report [PDF] here.

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