If you don't include the Toyota Prius, then a whopping 78% of hybrid owners switch back.
The main reason is due to the price premium of hybrids, which can take a decade or more to recoup through lower fuel costs. Other than the Prius and Lincoln MKZ, most other hybrids are just not cost-effective.
Many consumers end up buying a hybrid for emotional reasons - they want to help the environment and feel good about it, but if that's the case, then it makes more sense to buy a fuel-efficent used vehicle. The production process to create a new hybrid vehicle ends up hurting the environment way more than driving a higher-mpg used vehicle.
As an alternative to hybrids, you may want to consider buying a vehicle with a diesel engine or opting for one of the "super" fuel-efficient eco models that are hitting showrooms.