Google requires that all ads should be labeled with "Ads by Google" or some other form of label so that people know these are ads.
The top, one line ad on the LinkedIn page is not labeled as such. There is an ad unit on the right side, in a box, that is labeled correctly. Here is a screen capture.
As you can see, there is nothing describing to a human user that this top link is an ad. If you mouse over the link, you can see that the destination URL takes you through a Google AdSense link.
Is this against Google's terms of service? I assume they are a premium publisher, but even premium publishers are required to mark the ads as ads.
Forum discussion at Search Engine Roundtable Forums.
Side note: If you want to connect with me, my profile is at http://www.linkedin.com/in/rustybrick and I think you can email me at barry.schwartz at gmail dot com to connect.