I interviewed at Google quite some time ago, back in 2009. It seems like their process has gone heavily downhill since then. I wasn't given an offer, but I was only subjected to two phone screens (one recruiter, one technical), and then had a day of in-person interviews. One interviewer seemed a little dickish (or perhaps just didn't feel like being there), but the rest were overwhelmingly positive, and were fun and interesting to talk to.
The process wasn't quick, but it didn't feel long and drawn out, either. If I had to wait weeks between each stage, and was expected to pester my recruiting contact for status updates, I wouldn't bother with it at all. I get that it's different when you have to deal with remote interviewers and recruiters, but there's still no excuse for stringing people along like that.
I believe the interview process is the same today as what you experienced but probably more difficult. As that's what I've experienced at FB/Google/etc.
I think this person wasn't performing to the same level as some other candidates and that's why they kept getting asked to do more phone interviews. Google tends to only want to progress you if they believe you're going to succeed in the next steps - otherwise, what's the point? In this person's case, I think they would've failed and that's what the phone interview filtered out.
Btw, most of these places are more than willing to speed things up if you tell them you have an offer. e.g. FB has a rule of "no meetings Wednesdays" and says they won't interview then. I told them that was my only option - they said, "oh, ok. Let's do Wednesday then!"
The process wasn't quick, but it didn't feel long and drawn out, either. If I had to wait weeks between each stage, and was expected to pester my recruiting contact for status updates, I wouldn't bother with it at all. I get that it's different when you have to deal with remote interviewers and recruiters, but there's still no excuse for stringing people along like that.