Why don't you trust Steam with your CC info? It's encrypted during tranmission, only decrypted when it needs to be, then forgotten, although Valve store the last 4 digits and a one-way hash, from which it's impossible to work out your full number. It's pretty damn safe.
You don't trust VALVe? Does this also mean you don't trust Amazon, Dabs, etc, etc ... OMG they're gonna steal my money! VALVe is so untrustworthy being a multimillion dollar company! Save the children!
and so on, and so forth
Seriously, just buy thru Steam. It's the only way u'r guaranteed to get DoD:S without payingout extra l8r.