It was a topic of hallway discussion at MeeGo Conference 2010. Several Nokia employees confirmed it. According to the Nokia employees, a device can never again be fully trusted once it leaves locked down, DRM protected mode, so "developer mode" was seen as a one way trip. I believe there was discussion of the news in a thread or two here.

If there's to be a developer Harmattan device followed by a consumer Harmattan device, I could imagine the second being the only one with a non-reversible developer mode switch. Or perhaps the developer device won't support DRM at all. It will be interesting to see what Nokia releases.