If I wasn't such a GrownUpGeek fan, I'd say that is not cool. So all that gets picked up is the content of the page and the page URL not sig links or links in the content of the forum.
If there were sig links or links on forum-posts they would get picked-up, they just get filtered out so you'll never see any.. Links to .ORGs like Mozilla, or other quality/helpful sites like for SpyBotS&D are allowed.. Like i said, the Mods are like hawks that love to eat spam..
As far as I remember, G only counts forum sig links as ONE single link.... as this type of tactic you're talking about, at one time, was popular. G shut that down, so I wouldn't bother. However, I do have an idea that might be helpful..... I can't for the life of me remember where I seen this, but SOME (probably very few) forum softwares operate differently, concerning the sig link. Basically, look for a forum community. Make enough posts to get a sig link out there. Then, go into your control panel and change your sig link. Go back and look at your recent posts..... is your sig link changed? If not, then it may be a good way to target many more pages in your site, multiple times. Problem is, you'd have to change your sig link every time the topic would change.... to get maximum benefit. But even if you did find a forum where it all worked out like that, you still have one more problem - All your so-called 'juicy' links come from one single domain, and google can definitely figure that out. Might be great for other search engines tho.
I just joined http://www.revenuesource.com/ - it allows signature links immediately upon signup - pagerank isn't too shabby either.