Know what you mean and I often send PM's to people who only post their own threads and contribute naught to others. In fact on several occasions this has lead to me closing someone's account on the site. Their PM replies are often a good guide as to their personality flaws. Some people seem to forget the adage 'give and you shall receive". Others just need a little push in the right direction and take the PM comments on board and start helping others out as well.
We also have a bit of unwritten etiquette that if you post a photo for critique, then give three other member's photos a critique at the same time.
Personally I also like to see that people can actually take photos. If all they do is talk gear and how great some lens is, etc, but we never see any of their photos, we have no way of knowing if someone actually skilled at photography, or happy to just talk the talk.
Here is an example (member details removed - and they have had their account closed). Recently someone posted a comment on a thread on AP:
DIGITAL CAMERAS ARE clever things, and one of their cleverest tricks is their use of histograms. These have the ability to show you a real time ‘tone map’ of the photo you have just taken.
Depending on your camera, you open the histogram on the LCD screen at the back and it gives a visual representation of the tonal range of the shot, with deep shadows on the left, midtones in the middle (e.g. greys and greens) and highlights on the right. As such, it’s both a handy visual guide and a diagnostic tool, showing you areas of the shots that are under or over exposed. You can then make the necessary adjustments to compensate for this.
The histogram can be turned on and off in an instant, giving you an illustration of how 256 levels of brightness are distributed in a photo. The darkest shadows are 0, the highlights are 255, and the line running from left to right shows the increasing brightness in your image. Meanwhile, the peaks in the histogram relate to the amount of colour information.
Their post had a lot more than this excerpt shows, including links to a site. Now funnily those links went to a site selling camera gear. But a quick search of google and I found THIS. Nice little bit of cut-n-paste plagiarism.
Owning a forum is not only fun and rewarding, but you learn to be alert for particular posting patterns.
So as the OP in this thread comments. Join in, CONTRIBUTE and learn. Cause eventually someone will notice that someone else isn't using the site as it is intended (Forums mean by definition a place of interaction).