By my admittedly limited understanding of how HTTPS/TLS works, the end user (me) initiates a connection with a remote server which signs every one of its messages with a public key. This public key can be verified (magically) by checking the certificate, which is signed by a CA that vouches for the integrity of that certificate.
The upshot of this is that if I trust a CA, that CA can sign any certificate and say it is valid and my machine will be just fine with it; if a rogue CA is added to the trusted registry of my computer, then anyone who knows that rogue CA will be able to get their cert signed and pose as - potentially - any website and perform a man in the middle attack.
My corporation has just added their own cert as a root CA to all computers in the network. Should I therefore assume that all traffic I send is compromised?