IF you have an accident the shards are particularly nasty. As an example, in collegiate Human Powered Vehicle competitions any CF cycle fairing must have an inside layer of Kevlar in the lay-up. They do not want the rider to be able to come in contact with CF should there be any sort of accident.
I vaguely recall (read: could easily be wrong here) that CF shards are not recognized by the body as a foreign material. So they will not fester, they have to be dug out.
Then there's the other lightening aspect, your wallet.