I think time will tell as to whether or not a probability of a quake (as part of a prediction) is relevant.

Also, the use of a probability indicator may be irrelevent as to whether or not the predictor may be scheming to use is as an escape clause if his/her prediction does not happen. It may have more to due with the earthquake mechansim and what any data may suggest in the way of liklihood....

True...it is a scientific trapping...and no doubt used with good effect as a whipping scourge to keep those prediction-mongers in line... :)

Note that lightning bolts may be viewed as singular events...do they have a probability associated with them ? Just a thought....

My 2cents worth....