Should social media drive traffic to your site?

I came across two opinions about social media that are quite different.

The first one goes like this:

"The point of using social media as part of a marketing or PR strategy for a small business is to drive traffic and generate sales." Peter Shankman, founder and CEO of The Geek Factory, a boutique marketing and PR strategy firm in New York City. Read full article HERE.

The second one goes like this:

"Facebook marketing is not about driving traffic to your web site. Keep Facebook users on Facebook." Online Marketing blog. Read full article HERE.

So, my question is this: Should social media drive traffic to your site or not?