LinkedIn is the #1 business social network by a wide margin.  Of the ~25.3 Million registered accounts that we track, ~20 Million have more than 2 connections. We decided to track more than 2 user connections since most folks just login to check things out when they get the first email invite. Of the 20+ Million users, only 1.9 Million (or 9%) have a blog (Or have chosen to add their blog to their profile).

Plaxo in comparison has 13% bloggers registered of their 16.7 active (more than 2 connections) users.

Xing the European business social network in comparison has 14% bloggers.

Now if you blog for business, you would get about 0.2% to 0.5% referral traffic from business social networks (based on relative comparisons). This is not a large amount, but it all adds up.

What are the top 5 reasons for not listing blogs on business network profiles that we heard from our informal survey of 15 bloggers who we know do not have their blogs listed on LinkedIn?

1. Did not bother to do it. Most people fill out their profile on an as needed basis, instead of all at once.

2. Did not know you could. Funnily enough many people who registered over 3 years ago with LinkedIn or Xing do not bother to come back and add their blog to their profile.

3. Not a significant source of traffic. The relative “engagement” of business social networks compared to others (such as Facebook or MySpace) is lower. Hence most users dont check them out very frequently. Even though LinkedIn and Plaxo have added “Status Updates” as part of their capability, they are relatively recent and over 80% of people still dont use them.

4. Blog is behind “closed doors” or is a private blog. This was the #1 reason given for not listing their blogs. Its unfortunate but true, most business blogs are within the 4 confines of intranets (yes they still exist).

5. Dont have a blog. This was the #2 reason. Although over 140 Million blogs exist and over 45 Million in English language alone, most “business folks” dont maintain an active blog.

Have you registered your blog with your business network profile? If not, why are you not doing it?

There are over 50 social bookmarking websiteswhich primarily perform the function of allowing users to bookmark, share and annotate the web. We track 10 of them includingDelicious, Ma.gnolia.com,StumbleUpon, Diigo,Backflip, Blogmarks,Clipmarks, Furl, Simpyand Buddymarks.

We wanted to capture the value and difference of these sites not as a user of social bookmarks, but more from the standpoint of generating viral behavior and target specific audiences. To that end we also wanted to make some recommendations on which sites provide you specific value and hence might be a better use of your time to target and nurture the users of.

The value these bookmarking sites provide includes:

1. Traffic increase: If you get StumbledUpon expect a significant traffic increase within a short period (bursty) followed by a lull.

2. Relevance and link priority: As users tag your blog post or web page, they add their own filters, which help you understand a) your brand perception and b) your relavance with that communities sphere of influence

3. Ability to understand and create your early adopter base. For our solution, it was relatively easy to find out the users who bookmarked the content, hence were very interested in the relevant solution and would be keen on learning more when the beta was available. We built our entire list of 1033 beta users to provide us feedback on our product based on who bookmarked us and who they recommended us to.

Here are the recommendations:

1. Most # of users: Delicious and StumbleUpon are way ahead of the pack. StumbleUpon users tend to be more casual users and the traffic you’ll get will be fast and swift. Delicious traffic is more like a simmering pot, but depending on your content can get you

2. Topic focus: If you are an enterprise software company, Diigo and Backflip have the most users with content relevant for that space. ForMusic, Furl and BackFlip do a great job, and for Lifestyle topics Blogmarks is the most extensive. Its probably a function of the initial users and their likes / dislikes, but the content relevance for those topics is the most in those sites. Health related topics makes Delicious and Clipmarks the best. Finance related topics are most frequent onFurl.

3. Speed of propogation (Virality): Although Delicious has the most users, StumbleUpon, Furl and Diigo have the fastest velocity to user traction.

What do you think? Which ones do you use and why?