Now if you were to ask if it would affect your business, then only you know that. Forums often indirectly help with SEo, in as much as people will often link to your site off forum in their blogs etc.
Hmm. Are you sure? I only link on forums and you know where I am on Google.
but all of your links are from on topic forums and you have MILLIONS of links . I bet you also have loads on in context links on forums rather than sig links?