yh sure.. will get 200 BL.. but if the forum thread contains sig not indexed will not get

Yes, but they are all rel=nofollow...... Google ignores them.

The sig links on this site are do follow.

It does give you links per each page that is indexed. But also take advice from someone who does some SEO for a living, Google looks at your "link portfolio" more than how many. This means google weighs it the same if you have 5 links on a website or 500,000. It is all about websites showing they like your website or trust it which brings up your rank.

Yahoo still counts the nofollow backlinks and MSN too! So you get the benefit there irrespective

Of course Don't forget to ping your post links in order to get index quickly by search engines.

If you are helpful and post intelligently you will get traffic from people clicking on your signature tag besides the backlink.

All the links will be there, but the question is how important they will be considered by SEs.

It depends on the quality of the forum... For example, a sugnature in sitepoint could give you a lot of backlinks..

I think Google will add more weight to a single contextual link within a topic discussion than it does with your signature links. The main plus point for me with regards to signature links is the actual traffic that it brings.

As mentioned above, it's good to join maybe 3 - 4 related forums and add your sig there too. Try and make a number of posts per week to each one, although it's not about spamming forums with pointless posts. Add value and only post if you have something valid, or of value to post.

Forum links will show - but carry very,very little weight - miniscule - unless the url forum link is based on your topic. Think RELEVENCE