And writer Paul McAuley says it may be about to happen again:

Sf publishing has always been a chancy, hand-to-mouth affair for most. It imploded again in the early 1980s, and there are signs that it's about to implode again. And because they can't hope for sinecure positions in creative writing in universities (although that's changing, now), sf writers have always been ready to turn their hands and minds to the kind of writing that can be churned out quickly and profitably.... While Silverberg et al were working in the titillation trade in the US, over here in the UK Michael Moorcock was editing New Worlds with one hand and writing Sexton Blake adventures with the other, while many of his contemporaries were writing westerns, biker novels and, yes, sexploitation novels. A little later, Kim Newman and Neil Gaiman worked for the British soft porn magazine Knave. And sf writers today are also working in comics and graphic novels, novels based on role-playing games (Kim Newman and a slew of authors associated with Interzone in the 1990s wrote innovative and highly successful short stories novels for Games Workshop), film tie-ins . . .

The question is, if SF publishing does have another implosion, where will authors go this time? Porn publishing has been even harder hit by the Internet than other genres. Where will the suddenly starving SF authors turn this time around? [Paul McAuley]

After summarizing what he perceives as the head-in-the-sand attitude of print magazine editors ("[N]aturally enough, the magazines’ various teams appear not to consider anything to be wrong [despite the declining readership]. They’ll provide what their remaining audience would seem to want, until they all finally die of old age, and then they’ll turn out the lights. And that’ll be it for the short-fiction sf print magazine as we know it," he writes), Ellis starts looking at the reasons why online magazines often get ignored by followers of SF fiction:

One of the reasons... is that we associate print magazines with an intelligent curation process overseen by functional salaried adults. That’s why so many people still look askance at the online scene as "not proper magazines." The people who believe that got their wish last month, when one of the editors of HELIX SF had his covers pulled as a bigot with clear psychological issues by a disgruntled writer. It gives credence to the bias, unspoken or otherwise, that a print magazine is a job of work and an online magazine can be thrown up by any drooling lunatic with access to the net and a credit card. A fanzine by any other name.

Regular readers will know that I like sending traffic to the likes of CLARKESWORLD and FARRAGO’S WAINSCOT etc from time to time. Aside from (patchy, beautiful) McSWEENEY’S, these are the places I look to for short fiction now. No real fireworks yet, no real movement, none of them seem to be really cresting the other in terms of profile, but the best work there has been head and shoulders over pretty much anything I read from ASIMOV’S, F&SF or INTERZONE (with one exception in the latter case) over the last several months... It’s time now, I think, to turn attention to the online sf magazines. I personally live in hope that, one day, some of them move from net to print, and create a new generation of paper magazines. But, regardless, it’s time to focus on them — on what they do, how they generate revenue, and what their own future is.

But will that future include spam-esque pornbabble, that's what we want to know.

SF MAGAZINES: Yes, I’m Here To Ruin Everybody’s Day Again [Warren Ellis]