> if they ride the wave of positive sentiment they've gained
It's interesting to consider what the impact of the goodwill many people feel towards Google will be on Google+. With traditional commodities (e.g. cars, detergent, etc.) companies are keen to maintain trust, a positive image, and so on, amongst consumers.
That seems to have been less a factor in the success of companies like Facebook, perhaps because what they offered was so new and compelling that many people were willing to overlook trust issues, ethical and privacy lapses, etc.
Perhaps social networks are now becoming a commodity, and as a result, these factors may end up being much more important. It would be fascinating if Google+'s success was less about the technology and more about how people feel towards the company - if people say, "I can get the same experience from product X as I can from product Y, but I trust the company that makes product X more."