Unfortunately I do have a client that started with Yahoo Small Business for his web hosting and we have been using WordPress so that he can make his own updates.
The issue we have now run up against is that WordPress 3.2.1 requires PHP 5 and MySQL 5 to work. Yahoo is only half-way there on supporting this because PHP 5 is allowed while MySQL 5 is not yet supported. So we are stuck using an old version of WordPress which makes our site susceptible to hacking, not something that you want to risk when running a business and depending on your web site to always be up and running.
When you search other blogs about this the reply is uniform, "Yahoo Small Business" is far behind the times and will not commit to a date for supporting the most popular blogging and web CMS platform in the world.
Sad, but true. You have been warned.
I recommend hosting with 1and1 instead, they are up with the times, support the latest WordPress, have excellent up-time, the control panel is intuitive and real people answer the phone to support you.