Genius or stupidity.
I am in two minds about this.
On the one hand, we don't really need another smartphone platform. There's Symbian, Android and Windows Mobile which are all open to any manufacturer. There's WebOS, iPhone OS and Blackberry OS which are all platform specific AND Samsung already has LiMo on some phones.
On the other hand, if Samsung are going to use Bada across the entire range, and actually cease producing feature phones, then it could be a runaway success. The perfect example of that is LG who have their own proprietary semi-smartphone OS on millions of handsets across multiple models. If Samsung have everything on the one OS and they make sure there's an on-device app store for every handset, they could make a killing. Yes, I'm aware that LG still have some handsets with Windows and Symbian on them, but that's because they need those devices in their lineup or they'd lose sales.
The difficulty however will be attracting developers to the platform to make all those apps, and for that reason I think they would have been better adopting Symbian (or possibly Android) instead of re-inventing the wheel. Keeping Android in their lineup, when it has no enterprise market share, just complicates things.