I think forum profile links are highly devalued. If you mean links in posts or signatures, I think it will mostly depend on the specific forum where you are posting. If you post on a "serious" forum with high authority, it will help. If you post on a crappy warez forum, and you share the page with spammers speaking of and promoting gambling, drugs, illegal stuff, etc, it may do mor harm than good.
Well, out of context links have little to no value since the recent updates. However, content specific links from high PR sources still hold some value. So, make sure that your links fit these requirements and you'll be golden.
Its totally depend on you means how you are getting backlinks from forum. According to me, if you getting backlinks from signature then it's totally spamming, but if you are getting backlink from relevant thread then it's still valuable..
Dont build links in blasts . Google picks that up as unsual activity and will penalise your site . Try and be consistent and you will be fine . Also dont only look at backlinks but do the rest of the seo requirements as well. On page , Content , etc
Backlinks are still good. That is unless you are posting to low quality forums that have very little authority. The penguin updates frowns highly on any type of black hat SEO practices. Natural posting to high quality forums will benefit you the most.
I think only if the forum is directly related to your niche. But i do not believe forum backlinks have much importance as they used to. Posting a backlink to a "Dog training" site on a Internet Marketing forum for example is not natural and google will devalue this.