Meetings should be kept short and to the point. Unfortunately, meetings in most companies aren't anywhere close to this. At my former job, some meetings took more than 2-3 hours, with way too many people at the table, many of them who didn't factor into whatever we were discussing. Most of the time, we ended the meeting being farther away from our objective than when we began the meeting.
Supposed to, yes. But few companies have a person who's job is as specialised as hers. Google is about efficiency and her job is to keep the meetings efficient and organized.
I can't tell you how much I hate the meetings I have to go that devolve into time wasting because there's no agenda etc.
Actually any project manager worth their pay knows they should be doing this.
But even if they do, odds are they're going to run into problems of just trying to schedule meetings in the first place (hence regular, weekly meetings even if there's nothing to discuss), people unprepared even if an agenda is provided, and not having enough political clout to make sure that the everyone who needs to be there actually is or to shut someone up who's wasting time.
Mayer is in a position where she's not handicapped with those issues. Most executives wouldn't be either. The question would be are the rest of the meetings at Google this efficient?
