As sites like Twitter, Facebook and LinkedIn (and many many others) try to create shareholder value, the pressure on users of those sites continues to increase. But as always, it is as much about time as it is about utility.
While we use things like Twitter and LinkedIn as part of our marketing strategy for Design Nine and WideOpen Networks, we have low expectations. There is only so much time that any one person can spend on these sites. For example, LinkedIn has done a fair job of aggregating useful information, but it's the proverbial "drinking from a fire hose." You could easily spend many hours a day just reading postings on LinkedIn, and if you have take your job and your work seriously, you just aren't going to do that.
When LinkedIn first introduced the Facebook-style interface, a lot of people began posting, but over time, I watched the frequency of those postings decline until there is very little new content being added in the half dozen or so groups I joined on LinkedIn. Busy, productive people don't have time to "hang out" on Google Hangouts, LinkedIn groups, Twitter feeds, and the myriad of other Web sites clamoring for attention. It's a race to the bottom.