Yahoo allows your ad campaigns to be downloaded as a spreadsheet. Can you edit this and then upload it to alter your campaigns? How about Google, or MSN?
Both YSM and Google allow account downloads, but Google usually only provides this capability to agencies. This is probably because the agencies then need to send the altered spreadsheet to an account manager at Google or YSM to upload it. I'm guessing that once Google release an upload tool the download link will appear in all advertisers' accounts.