I have always found with credit cards that the biggest risk is...

I have always found with credit cards that the biggest risk is not having your number stolen online but giving it to retailers who then can use it to run up any bills they like and there is nothing you can do about it, it generally takes 9 months to get the money back.

Travel is the worst. I once had three airfares of people I never heard of run up on NW Air, another one on Qantas, a holiday run up twice. There is no way I would give my number to a porn provider who are presumable less reputable than airlines.

Currently I'm fighting a $150 Telstra charge from a porn provider who claims I ran up 30 minutes of dialer time. I remember the occasion - a dialer started to download after I killed an unsolicited email, I deleted it, but somehow it switched to their 055 number without mynoticing, though all I had open was the stock market. Telstra says point blank there is nothing they can do and I have to pay. I tell them they have become bill collectors for thieves and organized crime.