Maybe it's the allure of the KettleBell's having recently come out of the old Soviet Union and somehow Russian training methods and equipment are better than any thing else (not by a long shot). Or people just looking for new exercise toys, when actually the common DB might be better for most. Handling & balance for one. KettleBell's (shot/solid) have been around for over 100 years and might be considered the grandfather of the modern DB.
Montague may be right about the trendy idea, Americans are in love with things like that. After the craze of the Kettlebell dies down, they will go and spend money on to something new. Maybe it will be the hydro weight machines, isometrics with the rope and foot straps or old fashion cable stretching. Actually those three methods are not that bad for training, at all.
Surprise that some guy's, that post on GB, have not spoken up about their KettleBell training experience and workout protocol. They are spending money on them and buying books and video's, that's serious enough. KettleBell's can be good tools, just wonder how some might fair with the KettleBell vs DB workouts. Good Luck.