Liz Gannes reports via GigaOM on what Silicon Valley high schoolers had to say when prompted for views on tech and entrepreneurship:

As for MySpace? It did appear to be out of favor, with only one panelist admitted to using it regularly. Most of the students attested their main social network was Facebook, and said it would take a lot for them to change to a competitor. Only if a new service had extremely cool features that they couldn’t get elsewhere and all their friends were already on it would they change, was the consensus.

And from the comments, this snippet from Jonathon

MySpace IS out of favor, for quite a few reasons. For one, facebook has no ads, while myspace is loaded with them. For another, myspace tends to have frequent server problems and we often can’t log in or use it. The fact that myspace is so open in what people can put in their profile means that some profiles are loaded with bandwidth-sucking content- content that is poorly laid out and often useless. Facebook is clean, streamlined, easy to use, ad-free, and always running. Plus, facebook allows “wall-to-wall� views of conversations between users, whereas myspace doesn’t allow this easy view. Instead we have to scroll through everyone’s comments in two different windows or tabs. MySpace was a good “gateway drug� to social sites, but Facebook is the drug of choice. And yes, we do need to have our friends on a social network for us to join it; Orkut is great, but who else is on there from our generation? You can’t expect us to waste our time with something new if it hasn’t proven itself or shown itself to be potentially awesome. You guys created the instant gratification information age, and we’ve grown up with it. Most social networks don’t offer anything new or unique enough for us to bother.

These are useful insights.  However, I would always apply a little caution before fully embracing the rationalisations people offer for their choices after the fact.  It almost  goes without saying that Facebook appeals to the desire of a High Schooler to hang out in the spaces (once?) frequented by college kids. We are generally far more motivated by our emotions than our rational choice, especially when it comes to actions within a social context. The real reasons why MySpacer's move on to Facebook has probably as much to do with the reasons they don't articulate as those that they do.  But the issue of intrusive advertising certainly resonates with what been said elsewhere.  On that point, danah boyd, who spends a lot of time talking to teens, once summed up their perceptions of MySpace with a blissfully twisted turn of phrase when she referred to MySpace as "a zit full of marketing puss".