That advice only makes the situation worse. If you are applying to 100 postings a week, you are almost certainly applying to jobs you aren't qualified for, or don't really want. You're just playing the numbers game.
On the other side of it, HR departments are getting so many applications from unqualified people who are playing the numbers game, that eventually they just cut off the flow of incoming applications, qualified and unqualified alike.
I've often seen my son apply to great jobs that he is absolutely qualified for, and would be great for both himself and the employer, only to get a letter that they have closed applications due to the overwhelming response. If there weren't so many unqualified applicants pumping up their useless personal numbers, maybe he'd make the cut for interviews, where he can shine, and get the job. But he never gets that far because of unqualified resume spammers bogging down HR.
Everybody should do everybody else a favor, and just apply for the jobs that your are qualified, and want to accept.