"How can Google be said to control billions of desktops when the people involved can all switch search engines tomorrow if they wanted to."
I think you're missing the point. The billions of desktops don't know how or don't desire to switch engines tomorrow, that's the problem! I know someone who, instead of putting in company name and adding a .com to the end will fire up Google and put in company name in there, every single time. She doesn't know anything, because Google is the defacto and default search engine, hell, Google IS the internet. Therefore Google can promote ANYTHING and she will simply lap it up without querying it. This is potentially DANGEROUS.
What hope is there for others when Google has such a wide reach they can influence people at will to the total detriment of other companies?
"How can Analytics be said to have no competitors when anyone could write one tomorrow, or how about using Piwik or KISSmetrics or Clicky or Woopra or Open Web Analytics or FoxMetrics or ClickTale or Mint or GoingUp! or Crazy Egg or Mouseflow or Chartbeat or GoSquared or Moz Analytics or etc or etc or etc."
Have you actually tried to write a competitor site and then tried to actually get it promoted? When Google is the one controlling the views of billions of desktop, how do you think your company, who is a direct competitor, is actually going to fare regarding promotion when Google controls the view and, unchecked, will also stop you from being noticed at all?