I keep hearing the "got lucky" argument when describing Facebook and Zuck. All it shows is ignorance. If you study Facebook, you can seriously find very explicit product and culture decisions at each stage of its growth. These have little to do with luck.
I'd argue Zuck experiences the same share of luck as an average person does. It's what he has made out of his luck.
For example, a big evidence cited with the "luck" argument is how Zuck just happens to run into Sean Parker who introduces him to Peter Thiel. But the role of "luck" is over-stated: there are hundreds of people who run into Sean Parker. A handful of them even get introduced to Peter Thiel. But getting introduced or funded by Sean Parker/Thiel is not a ticket to a billion dollar company. There is much more to it having little to do with luck.