This is a very good and concise article that address this question very succinctly. The author tackles several often-mentioned phrases and claims of "god" or a miracle whenever something unexplained happened.
I often wonder if, when people say something like that, that they completely forgot about history, or are totally ignorant of the progress in knowledge. There are many things that were attributed to "acts of god", such as eclipses, earthquakes, volcano eruption, etc. Now, no one (other than Pat Robertson maybe who still attributes these natural events as "punishments" from god) would seriously claim such a thing.