Whilst reviews and guides are a useful feature for everyone invloved, users of the site, eBay itself, and the author - there are people out there who will willingly rip of your work.
Remember, under law, each article or guide that you write, is automatically copyrighted by YOU. You can put a copyright message on if you wish, but you do not have to, it is automatically assigned to you.
You have obviously given ebay permission to publish it on their websites, but unless you specifically say so in your guide, you have not given permission for anyone else to use the article. Ebay does not state anywhere that these guides are in the public domain, and copyright free, so copying them without permision is a no-no.
Some people are under the misconception that these guides can be used as a "free reprint" service so they can just steal the content and stick up a website and make money from adsense or other similar services.
That is not the case, the copyright for all guides rests with the author of the guide, and no one has the right, without the authors permission to use the guide.
Exceptions to this are the "fair use" rule, which allows quoting of small parts of the guide or review, if it is in context to another article written by someone else.
Remember, your work could be copied and put on any site, even ones you dont approve off. You can use google to search for copies of your guide, and if required, you could take legal action against any intellectual copyright theft.
There is nothing wrong with using real "copyright free" resources to build a money making site, but it is wrong to rip of other peoples work, without even having the decency to ask first. Not only are they making money of the backs of others, they are creating lots of duplicate content on the web which will be penalised by the search engines.
The worst part of it is, there are free resources out there, so why people need to take work from sites that DO NOT STATE THEY ARE FREE FROM COPYRIGHT is beyond me? Is it simply pure laziness? Greed? Who knows.
Whatever the reason, keep an eye out, its your work if you wrote it, and you have the right to decide who profits from it.