The first post on my twitter account was "what is this and why would anyone want to use it?"<p>It was definitely not "this is precisely the thing that I had been hoping for 10 years somebody would code up."<p>If you had tried to estimate the number of potential twitter users by counting up the number of people in the world who were search for a service that would publish their SMS-length plain text messages on a web site, you would have gotten nowhere meaningful.
It's an excellent article overall. I didn't realize the search count include the adSense matches (#4). Searches from Google's partners should still be counted though; presumably the end users search the term on the partners' sites.
I think the author means "target audience size" or "nr of potential customers" instead of "market size". A market size is usually expressed in money.<p>For many startups --as they often operate on new markets-- the size of the "target audience" is probably more interesting. In the markets the 'size' (in money) is also quite hard to measure. But in developed markets the 'size' is probably more interesting.
Why not just use the search based keyword tool? <a href="http://google.com/sktool" rel="nofollow">http://google.com/sktool</a> ?<p>Always seemed more accurate to me.