I was going to integrate wordpress mu in to my site, integrate it in to the SMF forums and everything, until I read the message on the installation saying that it won't use www. After not finding any option to disable this behavior on the admin panel, I figured I'd try a quick attempt at getting around this, and when it was unsuccessful, I decided to just can the whole project.
This software is nice no doubt, but you can't expect to be able to just bend other webmasters to your will. For some people, me included, changing the rest of my site and files around to not use www. would require considerable work as I've done a lot of custom modifications to the forum and I coded the rest of the pages myself.
When you also consider that the size of my database(57MB), it would be a chore to download it, find/replace, reupload and wait for phpmyadmin, only for a possibility of it to work.
This type of forceful marketing for a small third party internet movement is highly unprofessional, rude, and a straight up douchebag thing to do. I wouldn't mind a link or small image, I'd be able to easily remove that, but doing this without having an option to disable it is certainly the worst decision in the history of wordpress and I would bet that you lost a lot of potential users. WordPress might be the best and most used blogging software out there, but by no means is it the only software.
This is going down on my web site as one of the worst software experiences I've ever had.