http://www.msnbc.msn.com/id/34611930/ns/business-autos/

Chat rooms such as Priuschat.com dedicated to Toyota’s fuel-efficient hybrid are peppered with concerns raised by owners of the third-generation Prius, which was launched for the 2010 model year. At least 33 complaints alleging safety problems with the '10 Prius, most often involving braking issues have been filed with the National Highway Traffic Safety Administration’s Office of Defects Investigation.

NHTSA confirmed receiving complaints, which are a matter of public record, but would not comment further. A Toyota spokesman said no formal investigation is under way, but added that Internet traffic and other complaints had made the company aware of the concerns

Another good reason to own a Civic Hybrid.

 

This isn't unique to the 3rd Gen Prius. My Gen 2 Prius had the same issue. My '07 Camry Hybrid has experienced the same issue.
The reports are totally blown out of proportion. The car does NOT accelerate, the engine does not accelerate. Basically when a wheel looses traction when regenerative braking is in effect (tire goes airborn over a pot hole, slips on wet leaves, wet RR crossing) the car switches from regen to the physical braking system. There is a sub-second feeling that the car is accelerating but it really is not it's just the momentary change in braking effort during the transition. No big deal.

 

Chat rooms such as indianhomeappliances.in dedicated to Toyota’s fuel-efficient hybrid are peppered with concerns raised by owners of the third-generation Prius, which was launched for the 2010 model year. At least 33 complaints alleging safety problems with the '10 Prius, most often involving braking issues have been filed with the National Highway Traffic Safety Administration’s Office of Defects Investigation.