I carry my credit cards without my signature on the back of the cards. Here in the US, it's totally fine to put "see I.D." on the back of a credit card instead of a signature. So, when a merchant wants to verify my identification, I will simply give her my photo I.D. (driver's license here in the US). For me, this seems more secure than checking signatures because a thief can forge my signature easily if he has stolen my card.
If I bring these credit cards with me to Europe, will I be in trouble because there is no signature on the back of the cards?