SEO is a very vast field and it is very important for the SEO Experts to be updated with the latest updates. I heard that the back links for any website from the article submission sites, blog commenting sites, and from some other means like social bookmarking, classified submission, yahoo question answers are considered as spam. Is it correct??? Please anyone give me some information about it???
Where did you read about this, Is there any new update from Google, if you have any please forward your link for these updates.
Are you referring to the last blog post from Matt Cutts (found here)? In any case, there is no need to generalize the issue. He's simply pointing out at the spammy practices out there for link building purposes. Adequate guest posting, blogging and so on, with great content and made for relevant audiences has nothing to fear. Just read closely the last paragraphs of his post, there is no need to worry if what you're doing is correct and most of all, organic.