Well, taking this community as an example, I think WordPress is a perfectly good choice for building an audience and then a community. What we can learn from steve is that it matters less what technology we use and more how much value we provide and how well we execute.
Wordpress doesn't have an integrated forum module, but one can be added later, as Steve has done, when the readership and traffic of your site warrant it. And there are plenty of options; I personally like
Get Vanilla! because you can integrate the look and feel better. But vBulletin is tried and true.
The bottom line is, the choice of technology is not that important, just go for it!