Why do people continually compare Facebook with LinkedIn?

A recent analysis on Mashable.com (http://mashable.com/2011/12/03/linkedin-boot-camp-infographic/) compared the "user-friendliness" of LinkedIn to Facebook. I don't quite understand why people and the media have a focus on comparing two social media sites/tools that actually have very little in common. Yes, they are both in the social media space, and they are both about online networking and communication. However, there are many reasons why they can not be compared apples to apples. It does not matter that LinkedIn only has 135 million members, a small fraction if compared to Facebook. That is because LinkedIn is about professionals and business networking. If the company had a target of building a base to even 25% or 50% of Facebook's membership, the company would need to dilute the membership details, and the actual business experience because there are not that many business professionals in the world. While in the same sector, the two companies should continue to for us on their specific goals, aligned with the needs of their users and shareholders. NOT in the realm of competing with and trying to outperform fellow social media sites. Let's see if this takes hold.