Well, of course they will. Aren’t rules made to be broken? I disagree that there is no value in social networking. Social networking in the classroom (not necessarily Facebook) can help students learn how to interact with one another in a respectful and focused manner.
I’ve been using Edmodo this semester in my Digital Composition class (students and their parents sign a tools agreement form that explains how outside-the-district sites will be used) so students have a place to chat and plan, both in a large group and in small groups. The layout is reminiscent of Facebook, but without some of the features that students might abuse. I prefer the layout and flexibility of it to Moodle discussions and teachers can award students virtual badges for good behavior. Edmodo is not blocked, so students and teachers can easily access it. There is also an app for it.
Before long I will have those same students create LinkedIn profiles. Why not use the power of social networking to help them create a more professional online presence? The LinkedIn profiles will have links to their work from this class, letters of recommendation, and a link to the portfolio they will be creating in WordPress.