It is common in American English to refer to a powerful person or organization as an 800 pound gorilla. The expression makes sense -- a gorilla of that size would certainly be intimidating -- but what's so special about the number 800?
Seaching "n lb gorilla" on Google for various values of n results in many more hits when n = 800 than when n is any other quantity. Also, the Google Ngram Viewer finds notable occurrences of the phrase "800 pound gorilla" in texts starting around the late 1970s; other sized gorillas don't seem to be mentioned at all.
The Wikipedia entry for the idiom claims that the phrase is rooted in a riddle ("Where does an 800lb gorilla sleep?") but that's just passing the buck. A 700lb or 900lb gorilla would be equally entitled to sleep wherever he wants to.
Interestingly, the Wikipedia entry for Gorilla states that the average male gorilla weighs about 400lb, occasionally reaching 500lb in the wild. Only obese gorillas in captivity have attained weights of 600lb. So the number doesn't even seem to be related to gorilla biology (except that it is safely larger than any known gorilla, save King Kong).
Given that it's an arbitrary figure, is there any reason the number 800 would be more popular than any other? More generally, is there any relevant research into why some numbers would be more popular or pleasing than other in contexts like this?