in most cases what most people perceive as motion blur is not caused by the display but by the source material being watched, this is why these same people believe that 120/240 hz TV's have less blur because if you use their motion enhancers they reduce and sometimes even eliminate most all motion blur
if you want test for blur caused by the LCD panel itself you cannot use films or even most TV shows because they are mostly shot at 24 or 30 fps. this is the source of the blurring
its been long known that 60 fps is optimal for the human eye to perceive smooth motion. the vast majority of TV/movies etc. has been produced at half to less that half of that frame rate.
play video games on your TV and then tell me it blurs, i play PC games on my 60hz 32" sony TV all the time, i've been gaming for over 10 years with use on CRT's extensively, modern LCD panels rarely blur anymore witch is VERY easy to spot when they do because images don't blur but the SMEAR across the screen its very ugly, often certain panels would exhibit this problem with a certain color or color shift.
120/240 hz are not necessary for most people, but if you wish to spend the extra cash it can be nice to have for films mostly but they can enhance the appearance of just about any video type if your into how it makes things look