Please check out this thread:

http://www.fodors.com/forums/threads...p;tid=34475312

Last year I emailed my credit card number to the hotels in Europe with no problems encountered. However a family member in the IT business advised that I should not do that as email is very insecure. This year we are returning to Europe and, instead of emailing my credit card, I've called the hotels following my initial inquiry. In each case the hotel had my initial email inquiry so were able to very quickly confirm the reservation and take my credit card info.

This does not solve the problem of security - but I have a CC with a very low limit which I use for all bookings, shopping etc. on the Internet. So far it has worked perfectly!