see, I wonder about this. After speaking with Dave about it, and looking at what comic-buyers do, I'm not sure that "Author" necessarily has anything to do with it.
How many people buy "Spider-Man" or "Batman" comics? It doesn't matter who's writing. Others buy every Star Trek/Star Wars/Robotech/Buffy/D&D novel. I think SFF fans have brand loyalty more than anything else. It looks like Author-loyalty because in something like Wheel of Time or Shannara, one author has written all of 'em.
Now, I'm not saying there's NO author-loyalty. Asimov's success would directly contradict that, I'd think. And many people tried Magic Kingdom: For Sale because they had read Shannara. But I think they're, as a whole, more interested in a character/setting than they are in a writer.
Which leads to my dreaded "that's cool" phenomenon. THe more over-the-top and implausible, the cooler it is. "He blew up the entire planet," said with wide eyes and a racing voice.
And actually, this last part, while too often taken too far, is a development from a good trait: The fans are interested in the dieas, not what others are reading. If they're interested in ideas, then they're reading more avidly, and actually exploring. And that's good.