I'm besotted with Facebook. I can see it becoming the primary way that I -- and many other people -- interact online. So if you aren't on Facebook already, join now. Now.

Still here? Don't tell me, you need actual reasons to join. Fine, here goes:

• It's huge, and it's growing. While Facebook started as a network for college students, it opened up to anyone who wanted to join in September 2006, and grew more than 75% -- to almost 25 million users -- by February. I haven't found numbers more recent than that, but I can say that between 1-3 people in my own personal address book (1500 email addresses) are joining every day.
• Your friends are already there. If you import/connect to your address book when you sign up , you'll discover all the folks you know who are already on Facebook. This is a great way to keep in touch with them. You can even find out who in your universe is already on Facebook, before you sign up yourself.
• It mixes business with pleasure. Unlike LinkedIn, which feels like some sort of massive résumé swap, Facebook brings a personal side to its user interactions. More than half of my Facebook friends are colleagues or professional acquaintances, and now I'm finding out about their personal passions as well as their professional pursuits.
• It's one-stop shopping. Facebook offers blogging, photo sharing, messaging, web-to-mobile communications, social networking, and groups.
• It's a window on your world. Once you've added your contacts to your list of Facebook friends, your Facebook home page will be the best place on the web for you to find out what's going on with the folks you know. My favourite part of Facebook -- the thing that makes it truly addictive -- is checking in to see what's going on with all my friends and groups. I can see my friends' latest status reports, their latest new friends and groups, their notes, their photos....all in one place. The best way to get how cool this is is to take a look, but I don't think I can really share a screenshot because that would mean sharing details on my friends' activities. And that underlines what is so great about the Facebook feed: it feels far more personal than what you'd normally see on the wide open web.
• It's pretty. God knows, I've fallen in love with my share of social media tools, but most of them have required me to look past a barebones or even downright ugly interface in order to appreciate the inner beauty of content sharing, social networking, or whatever. In contrast, Facebook has a very polished interface.
• It can help you connect with your community. Facebook has now got an API -- application programming interface -- that lets people extend Facebook with all sorts of little applications and enhancements. (Check out some of the options so far.) And that API is going to see Facebook integrated into more and more 3rd party sites. If you find it easier to connect with your members, supporters, customers or friends on Facebook than to lure them into registering on your own site (and for most organizations, it will be MUCH easier to connect via Facebook) you need to start thinking now about how you can integrate Facebook's community and functionality into your own site.

I'll have more to say about Facebook -- and especially about the options for integrating Facebook with external web communities -- in the coming weeks. But if you want to understand why this matters, you need to join Facebook now. And once you do, be sure to add me as a friend!