Helps quite a lot i'd say. But be careful if you buy from some1 who has too many posts and the search engines see a sudden surge in your link count, they have a tendency to treat you as spam.
I'd say it's worth to it pay someone with thousand of posts for their signature. It'll surely bring you traffic and some inbound links.
That's good to hear. I got quite a lot of posts in quite a lot of forums, not all related though. Do unrelated forums pose a threat of any sort?
it's almost useless. If you post too much in a forum with your sig, you will be banned as being a spammer.
Its good for ranking higher in SERPS and its also good for traffic if the forum is related to your niche.
Don't think forum signature ads are worth posting for, but forum advertising is VERY effective. Back in 2005 before I knew anything about how the web worked, I ran a business entirely based on forum traffic. Google? What's that? Forums are great but not sure if a signature is worth paying for.