I really like Yahoo's PPC service but one thing it needs badly is the ability to add negative keywords to the campaign level. For me, adding them to the Adgroup level is not practical as I often have hundreds of adgroups per campaign.

Adding negatives at the account level is not practical at all. This is because some negatives do not apply to all campaigns.

Again, Yahoo's a great service but please allow advertisers to add negative keywords to the Campaign level.