Martin launched a new range of 'eco-friendly' acoustics last year using resin-bonded wood particle laminates to mimic the feel and tone of real wood, but I'm sure it wasn't DIY-grade MDF they used. Martin have such a massive reputation and history to protect, its a bold move but they seem to be biasing the marketing on the eco-angle and of course the lower price bracket. As far as i've read, they are very decent sounding (and feeling) guitars. Not had the chance to play one in person yet.