It has been a while I am waiting for such a feature. Same thing that the list feature on Twitter, Those two main social media are getting new synergies. LinkedIn is a great service that enables first to create an online profile, or extended resume to promote online, and secondly, to connect with your business network. But one of the weakness of LinkedIn was that it was static, meaning there was nothing on your profile that would evoluate in such a manner that it would drive users to go on their account on a daily basis. For example, the Facebook power, and the reason why it is so attractive for brands and advertisers, is that users owns a feed of actions and events which convinces people to check often what is going on. The same thing for Twitter. This is the Instant Web.
Now LinkedIn already had great other features that have been added over the time. For example the question and answers feature was pretty nice, but still limited I believe. Now that you can post your Twitter feed on LinkedIn, it makes your resume/profile interractive, and shows out what you are at the moment.
Now there is still some other features that I miss on LinkedIn. Especially, all the features that are dealing with groups. At some point, I was developping the alumni association of my master at Dauphine. But compared to Viadeo's hub feature, where you can add up job proposition, creates forum or even have a calendar of event, LinkedIn has limited options.
Hence, I believe that LinkedIn should boost this part of their business to enable people to create great private business groups. But I believe it will be on soon...