Yes and no. Most social bookmarking websites keep your bookmarks on their site, but over time these bookmarks can be pushed into archives and deeper pages. A permanent link sounds like one that would stay on the same page with approximately the same PR. So the links may be somewhat permanent, but they don't necessarily stay on the same page. Some social bookmarking websites simply remove links after they have been up for a while. Many people on here have noticed that social bookmarking often only gives them a temporary search engine boost. Something more buzz worthy may get better results with social bookmarking.
Articles eventually fade too, but it takes much more time. It depends on how you distribute them though. The ideal situation would be that you are providing an article for a quality related site. In that case the article would retain its benefits for quite a while. If you instead submit that article to hundreds of article directories, you will get a stream on new links as each article directory takes a different length of time to review and approve the articles. In this case, some search engines may block out most of the links as duplicate content. Over time webmasters will gradually republish your article giving you more links. All of these links will eventually move to deeper pages and get archived too. So in time they might not provide much seo help.
in time, as links are burried in archives the backlink value is a lot smaller. Social bookmarking sites are good for SEO from other reasons: if you have a quality article that will reach the front page for example, many people will link that article in blogs, forums and those links are do-follow, many with the right anchor. So... if your articles get popular on social bookmarking sites you have a lot of chances to get free backlinks from people that liked your content.
Some people afford lot social bookmarks,i think most of them could give you backlinks,but only a little could give you traffic.
Digg.com is great for bringing traffic and stumbleupon.com will also help a lot! I receive around 120 unique visits a day from digg alone and I get about 60 a day from stumble upon! So regardless of Backlinks provided by social networks they offer great benefits to those that submit! But, it's all about who you know! You need to build a strong friends list on both digg.com and stumbleupon.com to really see a major increase in traffic! Oh, and if you happen to become popular with one of your post it will be featured on the main page of digg!
The backlinks are particularly beneficial if you are trying to build PR, or get your site indexed on google. I reccomend bookmarking every relevant page on your site, and also any articles you have on article sites. Its all about exposure.
The problem with these social bookmarking sites is that your real URL is masked. They provide a redirect to your real URL. So, search engines don't see your real URL.
yes and No. There are many social bookmarking website which provide permanently backlinks i.e it stays forever. Whereas most the social bookmarking site pages are expired after some period of time. so its on you to decide which are better to go for. As far as my concern you should look after both aspect.