Credit Karma made headlines this week as the first company to offer free credit monitoring. The service includes a once-a-day check of your TransUnion credit file, and if there's any "significant" change, you'll get an e-mail. Significant, by the way, means a late payment, new account opened or a credit inquiry. 

According to company CEO and founder Kenneth Lin, Credit Karma won't ask for a credit card number, there are no hidden fees and the company won't sell your personal data. All they need at sign-up, Lin says, is the last four digits of your Social Security number. If you are one of the 10 percent this doesn't work for, you'll have to surrender your whole number.

It should be noted, however, that the company will likely use your registration profile to match you with offers from its marketing partners, although the partners do not see your credit score or file. 

Obviously there's a big hole in this protection – they only monitor one credit bureau. In order to effectively monitor your credit, arguably, the best way is to monitor all three credit reporting bureaus. If you want to monitor your Experian credit report for free, you can do so with Credit Sesame, which is also free. 

By federal law, you are entitled to a free copy of your credit report annually from each of the three credit reporting bureaus, including the aforementioned two and Equifax. You'd probably be much better off doing this, and signing up with a paid service that monitors all three if you feel you need the extra protection. 

If, however, you don't feel that's necessary, the freebies offered b Credit Karma and Credit Sesame are okay. Just weigh your options carefully and determine what will work best for you.