tedster - 5:23 am on Dec 15, 2012 (gmt 0)

What percentage of the websites controlled by www members are big corporates, and what percentage are sole traders and hobbiests

I work with both types of sites, and as far as I know, an SEO worker can never actually "control" a big corporate site. You can guide and train the various internal teams involved - and as the company gains some confidence in you you can get more rapid deployment of your ideas.

But even then, unless your contract come from way up in the C-level, you'll have some strong limitations. Even in-house SEOs for big corporates are up against it.

how many people... are in some ways crushing their own rankings by constantly clicking on the competition for the phrases they want to rank for?

The search phrases must be relatively low volume for that to have any significant effect, no?