I have been promoting one of my other sites recently and when I saw my latest 'Free' Google AdWords voucher (they're not exactly uncommon!) I thought I may as well give it a go. I have never used AdWords before so I went through the sign up process with my voucher in hand.
I created my campaign and didn't mind the fact that that they wanted billing information before they could activate my account - but then I noticed that there was a 'activaion fee' of £5 in my case that I needed to ay in order to activate my account. I took another look at the ad - yup "Try it for free - £50.00* FREE advertising.