Goldman Sachs has given new meaning to the term “Facebook friend.” The global investment banking and securities firm has invested $450 million in the hot social networking firm, as first reported by DealBook. DealBook reveals that the deal values Facebook at $50 billion and that Goldman is also aiming to raise as much as $1.5 billion from its wealthy clients to invest in Facebook.

DealBook reports that over the weekend, Goldman clients received an unusual request in their inbox – an invitation to invest in Facebook, which industry observers say is likely to stage an initial public offering in 2012. According to DealBook, clients would have to invest a minimum of $2 million and would be prohibited from selling their shares until 2013.

Goldman Sachs ranked as the top global mergers and acquisitions advisor last year, ousting competitor Morgan Stanley from its stronghold, according to Thomson Reuters data released this week. Goldman advised on 370 deals worth $554.5 billion in 2010, compared with Morgan Stanley's 394 deals worth $538.1 billion.

As for Facebook, the social networking site eclipsed Google as the most-visited website in the U.S. in 2010, according to a recent report from research firm Experian Hitwise.

In October, Facebook unveiled a handful of new features including “Groups,” which lets Facebook members target their updates and swap information with cabals of their choosing. Facebook’s blog explained how the new feature works:

“With new Groups, we made it easy for you to build a space for important groups of people in your life -- your family, your soccer team, your book club. All you have to do to get started is to create a group, add friends and start sharing. When a group member posts to the group, everyone in the group will receive a notification about that post. Now I won't have to guess anymore about whether my parents saw the pictures I posted of their grandkids; when I post in my family group, I'll know that they've been notified about it and that only they will see it. Since information posted in my new groups is only visible to group members by default, I can feel confident about who sees what I post.”