Last night we copied/pasted several job configurations across servers, from QA to Production, and the Run Task As credentials didn't get copied. This makes sense because the tasks on the production servers don't use the same credentials, those credentials didn't exist on the Production installations of VC, and there would have been no way for VC to have set the values correctly.
We only realized this was a problem because we saw a popup window in the VC UI.
It's not a show-stopper, but it would be nice to have a warning that the copy/paste wasn't 100% successful right after pasting.