Science fiction is doomed! The genre is a toothless wreck, praying to overdose on its pain meds, says a gang of critics. (Actually, they're only talking about the books, and only the books shelved under "science fiction.") The reasons why SF is obsolete or pointless or dead depend on which rant you read. But here are the main ones:

• SF is now real life. "We are at last living in an SF scenario," Brian Aldiss said in a recent London Times interview. The article went on to paraphrase: "A collapsing environment, a hyperconnected world, suicide bombers, perpetual surveillance, the discovery of other solar systems, novel pathogens, tourists in space, children drugged with behaviour controllers - it's all coming true at last." It's like SF is a laundry list of predictions, and we've ticked them all off. What about colonizing Mars, though? Why do only the sucky predictions have to come true?
• It's been colonized by mainstream literature. Authors like Cormac McCarthy and Kazuo Ishiguro have stolen away our precious science fictional heritage and re-branded it as literary fiction. The literary establishment lavishes attention on these appropriating works, but ignore speculative fiction that has similar themes. And somehow, this will cause SF to wither into irrelevance.
• It's turned into pure fantasy. People get off on the "sense of wonder" in science fiction, says Bookslut's Paul Kincaid. Think of SF as a cosmic crack dealer. But over time, the wonder has gotten bigger and bigger, and authors have given up on trying to provide a rational explanation for it. So the science has become magic, and the SF has become just another kind of fantasy.
• The fanbase is ancient. "The literature of youthful, forward-looking openness... is graying," laments David Brin. At conventions, you see more retirees in scooters than kids. Is it because teh kids are too busy playing video games? Or is it that those older readers have created an impenetrable fan culture and a genre that caters to their finnicky needs? Either way, this demographic trend spells trouble in the long term.
• Rackspace is shrinking. Science fiction books are doing well as trade paperbacks (the bigger kind) but are in danger of losing their prominence as mass market paperbacks (the pocket kind), says Tom Doherty, publisher of Tor Books. That means fewer impulse buys at airports and drug stores, which convert new readers to SF.