It's actually never been asked before, Terronium, but it's something that I put thought into so I appreciate your interest.
The dots represent the members of the community, who are located all over the world - that's why they form the shape of the continents. While they are close together, they are not touching, just as we are also physically separated. However, we are held together by one common denominator (GT) which, in this visual representation is the outer circle (a symbol which also has many appropriate connotations). This creates the image of a planet, which is obviously very appropriate given the site's name. I created the "planet" logo in 2004.
Here's a look at how the logo has has evolved over the years:
