Personal Learning Networks are all the rage at the moment. As with a lot of “modern” things, they’re existed for a long time but have now got a snappy new name. It used to be called “advice from friends and colleagues”. But in the era of social media the word friend has taken on a new meaning. Social media has provided me with a lot of friends who I’ve never met and never spoken to. I’ve exchanged a few tweets with them, commented on or received comments on a blog article, or maybe read a few forum posts, and as a result these people are, in Web 2.0-speak, friends. A PLN can take advantage of lots of different services – Facebook is perhaps the best-known, Ning is also very popular and offers The Educator’s PLN, but there are lots of others, each with their own advantages and disadvantages. Of all the available services, the one I find the most fascinating (and the most useful) is Twitter. One of the most interesting things I learned about Twitter before I even tried it was that it is like Marmite. It polarises.