I have been asked about using Facebook a few times in the last couple of days so I thought I would post my advice/thoughts here for future reference.
I don't pretend to be an expert on such things (I leave THAT to the likes of danah boyd) but I can offer the following answers when it comes to Facebook:
Is Facebook a good marketing tool?
I don't think Facebook is a strong marketing tool, at this stage. I think though that there is no harm in having a presence on Facebook. In some cases I would recommend that a presence is set up, if simply to circumvent other more 'unofficial' representations of your organisation.
How do we do this?
The easiest and most transparent way is to create a Page for your Organisation. It doesn't cost anything and takes very little time to set up. I say transparent because Pages are essentially large, informal ads. By using them you are not in danger of over-stepping the mark of potential and current students' privacy or looking rather uncool. If you're not sure about how Facebook works, its etiquette etc, the easiest way to use it is through Pages. Once you have set up your page, Facebook users can become 'fans' of your organisation.
How do Pages / Facebook work?
If you haven't used Facebook before, the key elements to understanding it are:
Individuals become members of Facebook by registering and setting up a profile. Usually members use their real names and a surprisingly large proportion use an actual photograph of themselves. They build up their profiles by putting in photos, videos etc. They then become 'friends' with other people on Facebook and can communicate with them by writing messages on their wall (a message board) or by sending them private messages, among other ways.
Members can also form or join groups which have their own page on which people can leave messages etc. Some organisations have used groups as a way in which to communicate with prospective and current students. The idea of the Page formalises the relationship of an organisation beyond a group. Having said that, there is no way of stopping anyone setting up a page for any particular organisation.
Should we do it?
As I said earlier, I think one good reason to do it is to stop others from doing it. Like all online social networks, you will lose some control over your 'message' and 'brand' in that fans can write on the wall of the page. You can remove the wall and the discussion area but in doing so you are removing one of the oft-used features of Facebook and may then lose some of the benefits of using it. Essentially Facebook is a social network that enables communication from many angles. If you remove one of these angles it will be noticed.
So how do we control it?
Essentially you can't. You have to balance comment with brand-control. Basically you have to learn to let go. This applies not only to Facebook but to Flickr, YouTube and other content sharing and social networking sites. You can remove the ability for users to provide feedback but you also need to weigh up the response to such a move.
A watchful eye is required with all uses of social networking and content sharing sites. This is one area that people underestimate: the time it takes to keep abreast of what is happening across their presences on these sites. (This is where email notifications and RSS feeds come in handy but that's a topic for another post).
Having said that, Facebook is probably one area that is easier to control. The fact that there is less anonymity on Facebook seems to make people a little more cautious than on general blogs and YouTube, for example. It is much more closed space than other social networking sites. The current etiquette may alter over time, especially now that Facebook has been opened to all, not just Uni/College students.
There is also the whole area of Facebook Applications but I will leave that to another day. This is just a brief beginner's guide.