Facebook is a beast of many faces, and more and more marketers are realizing that it’s got the particular shape to fit their needs. With it, brands are accessing a more observable and interconnected user base, for a smaller cost, with quicker response times, all on a nimble platform that lets them quickly take part in the conversation without losing legitimacy or transparency (if done right).

But Facebook is more than just a social network. It’s a content aggregator; it’s a friendslist; it’s a contact book; it’s a photo-sharing platform; it’s a video service; it’s a gaming platform; and it’s an advertising network–all things considered, it’s currently one of the most exciting playing field for brands because, well, Facebook is the entire web–condensed.

Facebook Pages = Corporate Websites: This recently added feature has done so much to open brands up to their followers and potential audiences. Without logging in, consumers can view brand Pages on Facebook – (hopefully) more interesting microcosms of corporate websites that actually allow interaction, rather than a hidden contact page. Pages has allowed for companies to proudly proclaim their presence in a way that’s transparent, and, more important, very easily updatable.

NewsFeed/Notifications = RSS Feed/Google Alerts: Facebook brought the concept of RSS aggregation to people who never ever heard of the acronym. With consumers able to subscribe to fan pages and groups, notifications are way for brands, through regular updating, to feed constant content to their audience, even if they’ve never heard of Google Reader, or think RSS is a military organization best on world domination.

Wall Posts = Blog Posts : The bonus here? With RSS feeds already built in, your messages have a more consistent visibility, whereas a brand blog on an external corporate site may have a longer slog in developing a regular readership.

IM = Email: With Facebook still doing a decent job at keeping spam out of its users’ message boxes, the private messaging system within the service serves as a legitimate alternative to email–and a way for PR professionals to transparently reach out to influential users who might have an interest in sharing their content within their network.

Discussion Boards = Discussion Boards: With the sheer abundance of web forums on every topic scattered across the web, Discussion Boards on FB mirror their external counterparts, while keeping the exchange more centralized. With fan numbers clearly posted, it’s not hard to see which are the discussions that really matter.

Facebook Gaming = Social Gaming: Facebook games are as a sophisticated as flexible as their external counterparts, but with the capability to build in features that make them intrinsically more social, helping games find and keep an audience, and, moreover, generate a viable revenue stream, FB emerges as a very attractive ‘game console’ for both branded and independent games.

I could go on about the trends that appear to be making Facebook a younger, smaller, and in many ways, more focused version of its older sibling the world wide web.

Since the beginning of the year, we’ve had a lot of opportunity to work with brands in exploring what it means to market and create entertainment on the popular social platform, and people will continue to create and discover new ways to leverage and expand the world’s fourth most visited website–but the most interesting part will be seeing how this unique microcosm continues to develop in its own parallel universe, both alongside, and completely intertwined with, the web.