I recently was a victim of fraud in the form of someone managing to use my card or account details to buy things on various websites, including clothing shops, video game shops-AND attempt (my bank stopped this one) to pay for an Air B&B at over £600.
In the process of sorting this out, I told my bank I don't shop online a lot anyway aside from ebay, and the agent said 'so is this you?' and told me I had a £15 a month contract with some shopper discount website, and there is another similar one that has only just started being deducted. Apparently I'd accidentally ticked something while buying a train ticket, and when I looked into it, the other one was something I'd clicked while buying something from moonpig or funkypigeon!
I got in touch with the companies and luckily they're both refunding me as they can see I've never utilised these 'vouchers', but even though I am not well off, £15 is an amount I'd not noticed. I wonder how many others have done similar.
And I am usually so careful, it must be easily done and unclear.