I've been trying out Quora and Peerpong lately, so I decided to post some of my answers here. It's rapid response, which I typically don't like to do, but I've sucked it up and decided such thinking is foolish since I'm not a professional journalist. Anyway, my answer to the above question:
I would say additional factors are the lack of design and marketing influences in Google's product development process. Google's engineering driven culture is the reason for its success, but also a factor in its failure in some areas. I'm not saying Google should be design driven like Apple, but a little balance is good. I also heard some product managers complain how influence tilts towards the engineers.
And once you're behind in the market, spending on advertising is a good avenue to catch up (i.e. Microsoft's Bing) but this goes against Google's mantra of zero marketing spend. Only recently has Google started to spend significant amounts of ad/marketing money to compete in the enterprise space, but it could have done this with Orkut while trying to upgrade and improve it.
The amazing fact that is sometimes forgotten is that Orkut is a top 50 site worldwide, number one is Brazil and India, and essentially the business/name card for everyone in Brazil. This is done with zero marketing. Sort of a shame that Google didn't place more emphasis on developing and marketing Orkut early on while MySpace and Facebook were just starting out.