Really interesting question. I think it probably is not all that much and I’ll give you a reason or two for that. Number one, take a look at how many people follow, I don’t know, me or Danny Sullivan on Twitter or people that subscribe to my blog and the numbers that you end up with are about 50,000. So 50,000 people follow Danny, about 50,000 people follow me, about 50,000 people read my blog so what’s that telling me is whether you look at any popular blog, SEO related, there is you know, 50, maybe 100,000 people that are interested in the SEO aspect of things but compared to the millions and millions and millions of people who are searching every day, that’s still a relatively small percentage.
and I think a lot of tools within Google can do a pretty good job of stripping out, you know, queries that look sort of artificial, that are repeated, or you know come too fast or for whatever reason looks like bots so I think that even if we don’t strip those out, it’s a relatively minor effect but I think that we do strip out those relatively well.
Now, in certain fields, like you know maybe the query search engine optimization, that one might be a little bit skewed by people checking the rankings or you know various things like that but as soon as you get away from those head queries, more towards the tail, I think that they’re relatively accurate and I don’t think that they’re that skewed by the various search marketers and SEO’s and rank checkers and bots and all that sort of stuff so it might not be perfect but I think to within, you know, a relatively good percentage that stuff should be quite accurate.
by Matt Cutts - Google's Head of Search Quality Team