Is there such a thing as a free comic?

I've just been sent an email by wowio, an ad-based service offering downloadable e-books - including comics from UK publisher Markosia and others.

It all sounds fine and dandy but the stumbling block came when I tried it out, only to discover they want your credit card details to 'prove your identity'. Hmm... I think this is an interesting idea, but if it's really free, why do they need my credit card details at all?

Incredibly they advise that if you don't have a credit card, you can "have a parent or friend set up an account and vouch for you". Well, that's not exactly checking your identity, is it?

I don't really know who wowio are, even though they do publish a land address on their site. It just dosen't feel right, I'm afraid. This one gets a miss.

To their credit, I expressed my concerns in an e-mail and they get top marks for instant customer feedback. Here's their response in full:

"We use credit cards as a simple and practical means of authenticating a user's identity. This is important for a number of reasons: (1) it allows us to give advertisers accurate metrics--i.e., when we claim x number of unique people have downloaded their ad, we can be prove that it's true, (2) it allows us to limit the number of downloads per person per day, which allows us to manage the burn rate of the ad pipeline and ensure the continued availability of titles, and (3) it allows us to label the book with the user's name and other markers, which is important from the perspective of minimizing illegal file trading, etc.

"We use encrypted SSL to transmit all information securely, and we do not store your credit card number or related information. We check it once to make sure you are who you say you are, and that's it. We also will not share your personal information with anyone -- ever -- without your written permission.

"We understand the apprehension of many users to put in credit card information. It takes time to build trust. We hope we can earn yours."