WordPress accounts for something like 19% of all websites, more so than any other single platform. Do not underestimate the importance of their decision.
A bit higher, according to those who monitor these sorts of things.
Some 28.7% of sites use Wordpress.* Curiously, I've seen the 19% number being cited as 19% of all new websites use Wordpress. I'm not sure how 19% becomes 28.7%, but it may just be that sites using WP stick around longer.
