The approach has been around for a years (see my comment in that thread, for example), but very few of us use it.

The thing you'll run into with that approach is that no authors of gems and plugins that include AR models declare attributes as accessible, effectively assuming that mass assignment is enabled and resulting in the gem/plugin not saving properly. I've had to fork and submit patches for every hugely popular gem with AR models I've used, so it appears practically no one else follows this approach in production apps.

I strongly suspect that leaving all attributes mass assignable on all models other than generated user models is extremely common in Rails apps and it's very likely that this vulnerability is ubiquitous.