The headline ‘The Yogurt of Beers‘ piqued my interest when I paid a visit to Chow this morning.
The parallel with yogurt is due to the fact that Cask Beer is allowed to ferment naturally with yeast left in the cask until served.
This is also where the ‘unfiltered’ connection comes into play.
More and more wines are bottled unfiltered to keep that authentic feel.
The average beer drinker (‘give me a frozen glass’ type) will not fall for this as cask beer is served in the 54-57 degrees (Fahrenheit) range. 
As far as alcohol content, ‘Cask Ale’ can go from 4 to 12 percent depending on the type .
If you want more detailed explanations read What Cask Marque by Roger Protz which highlights the differences in the process.
For most American beers, carbonation is created by adding CO2.
One of the Breweries that serves Cask Ale using a traditional ‘English Beer Engine’ (pictured here) is Steelhead Brewing at their Burlingame (California) location, their Beer List is quite interesting.
Getting thirsty, you can also attend one of the ‘slow beer’ festivals listed in the Chow article and mix and mingle with the fans.
It’s a natural feel.
More Beer flavored stories: A Brazilian jam with Free Beer and Short for …Apple wood smoked Apple Ale