We know Yahoo! is working hard on a new paid listing web interface but now we got what we got. WebmasterWorld members complain over a Major Overture Interface Flaw within the Overture interface. Basically, when you set up new keywords, by default, YSM sets the bid price to the number one position. When setting up hundreds of keywords within the system, it is virtually impossible to go through each listing to lower the bid. Plus, it is clear from the thread that it is not easy to understand how to set bids when adding listings. Bottom line, new and even old advertisers are confused by the add listing process at Overture. For one advertiser, it cost them "$200 in about 3 hours" and a lot of frustration.
I just set up a keyword campaign of over 200 keywords yesterday but I did not personally find it confusing. Doing it manually is a lot of work, to set the bid prices properly. But if you are seriously going about adding hundreds of keyword phrases on a frequent basis, consider building a software application that works with the API Yahoo! provides. It will help you control prices and budgets.