SMF does NOT have NO FOLLOW as a default. Build many of these and stock it with cheap forum posters that linkwheel to your other properties. There's also SEO-friendly "nice url" mods you can use. Why do this instead of blogs? Cheaper content plus more topic coverage due to thread/discussion setup.
Of course, you would need to link to these from other sources to build up their link juice.
Configure your settings so it's easier for you to prevent, detect, and delete xrumer-based attacks though. Those V|4gr4 spiced ham comments and signatures do add up.
More info and discussion at
www.highrevenue.com