My little girl has her front dew claws. Although her show breeder had her tail docked to a medium length, she purposely left the dew claws. She does performance sports with many of her dogs, and she leaves the dew claws on all her dogs. She hasn't had any problems with her dew claws.
I read of the possibility of dew claws coming back, but now attached fully, if they were improperly removed.
This is an excellent article about the use of dew claws.
http://www.caninesports.com/uploads/...xplanation.pdf