A few months back, I ended my subscription to Equifax's Credit Monitoring Service because I found out that they only monitor changes to your credit report on a monthly basis. That's not good if someone gets a hold of your credit card number early in the monthly cycle. I was lucky in that someone got a hold of my CC number ath the very end of the cycle. As a result, I was able to nip it in the bud.
In the book "Scam Proof Your Life", the author suggests signing up for one of two credit monitoring services which monitor your credit on a DAILY basis. (Identity Guard or Privacy Guard).