One problem related to brake antilock wheel speed sensor has been reported for the 2007 Toyota Prius. The most recently reported issues are listed below.
Driving on a rainy day, abs and vsc lights on dash came on. My car violently fishtailed almost 180 degrees, back and forth 6 times on a curve getting off a freeway (about 45 mph) nearly crashed. I proceeded very slowly to side street. Car shimmied to right making a left turn. Felt like I was driving on ice. Called a tow truck. Dealership found rodent damage to wires to wheel speed sensor. I discovered manufacturers using soy oil on wiring. $1300 repair.