Counter to Wikimedia claims, their content is not free. At least, not in the sense of being freely reusable. The cost for reuse, in the case of text, basically consists of two requirements: 1 the Wikimedia origin has to be named, 2 the same two requirements apply for further reuse.
Depending on the situation, this can be near invisible or a major obstacle. For example, it hampers reuse is projects that are really free, while a republisher making money need only comply with the requirements, at the back of the title page.
The reason redistributing for money is allowed under these licenses is that they are intended to promote the distribution of information; they only stop people from copyrighting material and thereby stopping the free flow. That means that commercial distributors are in their right. And indeed, in a way they contribute, as they allow taking parts of Wikipedia where there is no Internet. Having said that, their prices appear a bit steep, unless these books are quite large.
When there's no attribution at all, the situation is different, of course. The idea of crafting copyleft licenses on existing law is that you can take indeed take someone who violates it to court. This approach has made the actual licenses very complicated, however, and as a result even most users who intend to comply can be argued to be at fault; Wikimedia a prime example.
I've never been fond of this existing-law approach. In my opinion we should have gone for a simple manifest of what copyleft was, and make it accepted in community as quickly as possible. That way it could have been introduced into law as general accepted practice
But, anyway, write in Wikipedia on the assumption that you're giving the world the text you write. That's the basic assumption and any other approach will cause you pain sooner or later. But if them guys are violating the license, then I hope they are taken to court. And that way we may also find out what these complicated copyleft licenses are worth.