Over the last few months, Twitter has removed the auto-preview feature for Instagram Tweets. So now you have to click through the link in the Tweet to see the photo. Presumably Twitter did this to encourage their users to use their native photo sharing application. When LinkedIn redesigned their profile page about a month ago, they dramatically decreased the exposure of a user's Twitter account. In fact, it's not even on the main profile page, you have to click "contact info" to see a user's Twitter account. This is a drastic change given the LinkedIn/Twitter integration that used to exist.
So LinkedIn is blocking out Twitter and Twitter is blocking out Instagram.
I think this is dangerous for LinkedIn and Twitter. I've written in the past about how difficult it is to build a successful B2C business. Your product has to be so great and so valuable if you want to win. You don't have the luxury of a salesperson whispering in the user's ear giving them context on your decisions or information about what's coming soon and how the product will improve. The product has to be great, right now.
Of course, I don't know all of the facts behind these decisions. But I do know that the effect of blocking out applications that users like is bad. And in a B2C business, what's bad for the "C" very quickly becomes bad for the "B".