I am running a portal site and it is observed that traffic is decreasing as compared to the competitors. I am trying to adopt new techniques that will help to increase the traffic. I am targeting many activities to increase the visitor count such as blog commenting, backlinks, forums, QA sites and much more. But on the other hand, is it compulsory to participate on social bookmarking sites to increase the traffic? If yes, then why is it necessary to participate and what benefit it will pass on to the site? The suggestion is welcome!! Thank you!!