For the past several years the rise of social bookmarking as a versatile tool for SEO and marketing has had a massive impact in IM. Bookmarking is heavily in use by online marketers for obtaining backlinks and more traffic. But you really should never neglect or overlook what can be done for the more long-term approaches at high PR bookmarking sites. So it all just depends on what you want to accomplish in your business. If you have not been around IM much, then a bookmarking site is simply just a site where you can place bookmarks on the net. Plus you can tag your bookmarks with your particular search phrases which can help with some SEO but it tends to be temporary.
Several years ago the more popular bookmark sites changed all their links to nofollow which had a huge effect on bookmark rankings. Seems people had the ability to rank highly from sites like Digg and a few others. Who really knows if Google had any influence over those powerful bookmarking sites and the nofollow relational attribute. It does make for fascinating speculation but not terribly important at this point.
Even so there is a lot you can do with certain approaches at these highly trafficked sites. Mass backlinking profiles at bookmark sites are renowned for being just about useless and even spammy. However, I am knowledgeable of people who do take a few more minutes creating their profiles. Profiles that have looks of being legitimate will do a better job for you and have a good chance of passing a review. This truly is the best way to go for many good reasons, and you will be able to use them for effective bookmarking for a long time.
When you do build a useful profile with content, then naturally you can create an RSS feed from that. You can market your RSS feed at other places and RSS directories. Consider the added benefit of more exposure for your links in those feeds. But you do have to be careful and exercise caution so you aren't over-promoting because that can cause loss of subscribers to your feed.
There is a balance that you have to keep with the amount of content and different marketing methods in your feeds. You can accomplish a lot if you have solid associations in place at bookmarking sites. It is best to maintain a respectful presence at social bookmarking sites, and if you do that then you will find it serves you well.
Ultimately, how you approach using bookmarking sites in your own business is your call. Most people are likely to just use them for backlinking, and it does seem that the approach outlined above is not used by so many people. However, there really is power in that approach based on the feedback we pick up from those who use it.