Via io9, an interesting observation from LibraryThing user bookmonkey00k:
Now Dune gives us a lot as well; space travel, economics, guilds, family drama, mysticism, desert people, sand worms, and martial arts. The problem, to do all of this Frank Herbert needed a lot of space, 517 pages of space, and to be fair, with the incredible amount of stuff Herbert put into the book, he needed all of it.
Now Dune went on to win all sorts of awards, and is credited by many SF fans as a personal favourite or even the book that turned them onto SF. My problem is the effect Dune had on SF as a genre. Basically, people looked at it and instead of saying, “Wow – you can have this kind of massive family drama/economic intrigue/war story/mystical journey all in the context of SF”, they said, “Dune must be awesome because it’s really long.”
So after 1965 all SF started to get really, REALLY, BIG. I mean, when I've lined up my copy of Dune with three SF books that had been written in the previous decade (Double Star and Starship Troopers by Heinlein, and Mission of Gravity by Hal Clement), all of them award winners, all of them critically acclaimed, and all of them barely adding up to the page count that is DUNE.
The trend of writing bigger SF books never stopped. Have you looked at the page count of recent SF? These things are monsters, often coming in at just under a thousand pages and the worst thing is a lot of it feels like filler, and I am not the only one to notice this.
I've never thought of substantial world-building is a liability -- and boy, did Frank Herbert bust his hump in the world-building process -- but bookmonkey00k makes a good point. It could be easy for a writer to substitute quantity for quality (a trend possibly reflected in the rise within the genre of sequels over stand-alone novels). And excessive length could raise the entry cost to a novel or a series, deterring many readers from starting.