The latest craze seems to be "Double IPA's". Many breweries have been putting out these types of beers lately, there is even a "Double IPA" Festival February 10th at the Bistro, 1001 B Street, Hayward, CA - 510-886-8525
Basically they are really big, really bitter, really hoppy IPA's. By 'big', I mean high gravity, high alcohol beers. Double is used here kind of in the tradition of say, a doppelbock in Germany. It loosely means 'a lot more body and alcohol'.
20 Tank used to have the biggest IPA around in the Moody's High Top IPA since the opening of the pub. Moody's was about 7.5%. Most IPA's are around 6.5%. Bridgeport in Portland has an IPA that's 5.5%! That's lower than many Pale Ales in San Francisco! So it is quite possible that Moody's was the first "double IPA" in San Francisco.
So many breweries have come out with very big IPA's to push the envelope. Magnolia was one of the first to push the hop envelope with the Proving Ground Pale. This beer is only 7% - relatively average for alcohol, but it is a projected 100 IBU's. Marin Brewing Company followed with the Eldridge Grade White Knuckler. Moylan's in Navato chimed in with their holiday beer which is a similar style.
Potrero Brewing Company also produced their Winter Wunder IPA (named after Wunder Brewing Company). It was an 8%, 90 IBU IPA. It wasn't necessarily brewed as a "double IPA", but more in the holiday spirit of giving. 15 barrels of this beer lasted about 3 weeks.
So the question is, how big and how hoppy are the beers going to get? The envelope keeps being pushed, and beer drinkers keep finishing the tanks of beer. I think IPA's became popular because they were the fullest flavored beers available. People simply got tired of the same ordinary beers all the time. And just like food in California, it's all about trying different things and creating something unique and over the top.
I think the law of diminishing returns applies to bitterness when dealing with these big beers. There comes a certain point where the wort simply can't absorb any more bitterness from the hops. But the amount of bitterness wort can absorb is also relative to the gravity of the wort. So a higher gravity wort can absorb much more bitterness (it can at least 'stand up to' the bitterness).
But I think beers will hit a limit on bitterness. If that limit is not already met, breweries may experience it very soon. If they go any further, brewers will just be producing very bitter barley wines (try Old Cornelius Barley Wine at 21-st Amendment).
I, for one, would very much like to push that envelope and try to pass that limit to see just where it is. I don't believe you know your limits until you pass them, so let's pass them. But I wouldn't call it a "double IPA". This is California. This is 'normal' beer to us.
But we are all about pushing that envelope and creating styles that have never been. So maybe this is in fact a new style. Maybe the GABF will create a new style just as they did a couple years ago for "American Style IPA". Maybe it will be called "San Francisco IPA", or even "Double IPA".
Whatever you call it, it is different, it is a relatively new "craze", and there is something very special and unique about it. It is something to be enjoyed (and fast - while the tank is quickly draining). So if you attend the "Double IPA" Festival, enjoy many of those great beers, just make sure you have a ride and you don't have to work the next morning!