LinkedIn, the professional social-networking site, may not best meet consumer expectations when it comes to the Ideal for social networking. But it certainly seems to be exceeding investor expectations.

Given the import and influence of social networking sites in marketing and consumer outreach, we added the category to this year's Customer Loyalty Engagement Index. While there are a lot of nascent social networking sites out there, only five brands were mentioned enough times to be included in the survey. They ranked as follows:

  1. Facebook
  2. MySpace
  3. LinkedIn
  4. Flickr
  5. Twitter

Foursquare, Quora, YouTube and Yelp didn't make the list. Neither did Friendster, which is in the middle of massive reorganization mode.

But being 3rd hasn't hurt LinkedIn, which has increased its planned IPO, valuing the site at more than $3 billion. It plans to sell more than $315 million of shares to expand their business, with 7.84 million Class A shares valued in the range of $32 to $35 each.

Is it worth it and is that where you want to invest your money? Well, how do others fare? Facebook is valued at $89.2 billion. So that's good. But MySpace is only valued in the range of $500 million to 1.2 billion, and that's not so good for a company that Rupert Murdoch paid $580 million for, so you'll have to be the judge.

One word of really good investment advice: the only safe – and proven – way to double your money is to fold it over once and put it back in your pocket!