Why do visualizers for search-engine results suck?

It seems like every three months or so, someone sends me a link to yet another visualization/association search engine — enter your search terms and get back a graphic display of likely matches laid out graphically so that you can point-and-click to explore the results and take various associated twists and turns.

Am I visually dyslexic, or do these roundly suck? I pull up the results to a simple query whose response-space I’m already familiar with (say, “Boing Boing” or “Cory Doctorow”) on an engine like Kartoo, and they’re completely mystifying. What do all those squiggly lines mean? Why is this close to that and far from that other thing? I don’t understand how this is supposed to augment or supplant Google. Link Discuss (Thanks, Dan!)