Now I can understand some worry about cd key generators.. but lets think here..
Take a look at half-life1, it needed a cd key, and there were loads of cd key generators out there. Rumors have it some people were able to use steam with a few of those generated keys. Odds are some perfectly legit people can't play online for that reason alone.
Now take a look at Half-Life2, there are no cd-key generators, why? because there is no installers. There isn't exactly an installer to hack and find keys for.
I personally love the idea of having everything done via steam, if I could have all my games run via steam I wouldn't mind at all.