I also faced the same issue when I booked with Sofitel Bali Nusa Dua earlier this year and Mercure Bugis last year. I NEVER will share my credit card details via Email, so I usually just give the hotel a call and provide it to them directly.
[MENTION=12993]amy[/MENTION] (AccorHotels Concierge) Would appreciate if you could get IT to take a look at this as if it happens to much, security might be an issue. (Would't want a Hyatt incident to happen)