Facebook, Twitter campaigns seen by consumer advocates as circumventing legislation aimed at protecting young people from aggressive marketing tactics.

The use of social media by credit-card companies has some consumer advocates looking for a "dislike" button.

Credit-card lenders are mining "likes" on Facebook and scouring tweets on Twitter as they look for new ways to entice existing customers to use their cards more frequently and raise their appeal among younger consumers.

But experts worry these platforms may give lenders another door around rules that took effect two years ago aimed at protecting young consumers. The rules, part of the Credit Card Accountability, Responsibility and Disclosure Act, were meant to curb aggressive tactics by lenders to sign young customers up for credit cards. The provisions limited certain marketing tactics on college campuses and required issuers to consider an applicant's ability to pay.

"The Credit CARD Act took the first steps toward protecting young people from unfair marketing by credit-card companies that often led them into excessive, overpriced credit-card debt," said Ed Mierzwinski, consumer program director at the U.S. Public Interest Research Group."We need more study of other marketing channels to see whether or not ... social media in particular is being used by the credit-card companies to get around the limits of the Credit CARD Act."

American Express Co. has been among the most aggressive credit-card lenders in tapping social media to promote its cards. The New York-based company has rolled out deals with Facebook, Twitter and social check-in service Foursquare that allow cardholders to earn discounts at merchants by syncing their cards with their social media accounts.

For example, participating cardholders can receive deals to specific retailers based on brands and activities they have liked on Facebook. On Twitter, they can have deals automatically loaded to their card accounts by tweeting messages with special "hashtags," or identifiers used to categorize tweets.

J.P. Morgan Chase & Co., Discover Financial Services, Capital One Financial Corp. and other lenders have also tested Facebook tie-ins or online games.