1) There seems to be an awful lot of "OMG! The students are doing something that we don't control!" Yes, of course they are. They have their own lives, and universities do not own them 24/7. Get over it.
2) "[M]ost [sixth-formers hoping to go to university] ... resented the idea that [social networking sites] might be invaded by academics." This is hardly a surprise. Most sixth-formers think of academics as being just like school teachers. Ask the same question to a bunch of first-year undergraduates, who have had time to learn that there's a difference, and you might well get a different answer.
That said, of course certain spaces within social networks are student spaces (though not, of course, Facebook itself - students have no more right to ownership of that than any other section of the population), and tutors should not barge in there uninvited. There are a couple of online student fora I read, and occasionally contribute to - but I'm very careful what I do or do not say, and not to assert any authority. And there are some areas within those fora into which I won't go. (As a result, I have apparently acquired a reputation as someone who is terribly helpful. But then these are OU students, who are different from the normal run of 18-22 year old undergraduates.)
3) "Because students are going on to Facebook and using it with their friends, there is informal learning occurring and students may be blocking certain people out of this." Yes. So what? If a subset of students go down the pub and talk about their lecture, there's informal learning going on, excluding those who aren't there. Should universities be insisting that students only go in the pub as a full group? (Difficult in a course with 100 + students, I'd have thought.) If a student reads a book not on the reading list, there's informal learning going on, from which all their fellows are excluded. An individual learning experience cannot be micro-managed in this way. Again, get over it.
5) "I'm on Facebook and I have a laugh with friends ... But, if it comes to academic work on Facebook, it's totally inappropriate." Twaddle. You can make academic use of Facebook, as I do, to network with other academics - academic networks are social networks too, you know.
6) "Students are using these social-networking sites, and they often appear less keen on using the virtual learning environment. In fact, [Jo Fox] suspected, the popularity of one was leading to her increasing lack of success in getting interactions going in the other." Again, is this a surprise? Students who are unresponsive in seminars may become very animated once down the pub. Worrying about what students are doing outside of class isn't a productive use of time.
The people who really wish this wasn't the case, of course, are the university administrators pushing Virtual Learning Environments, in the hope that it will enable them to stop worrying about scruffy lecture halls that eat all that maintenance budget. They don't want to be told why this will not work, and think that if only the students weren't distracted by Facebook, students would put all their energies into the university-approved VLE. It doesn't work like that. Don't get me wrong, I think the VLE can bring much (particularly in an institution like the OU). But it isn't a magic solution to all problems, and needs to be treated as a supplement to other parts of the learning experience, not a substitute.