There's been too much sad news coming out of Yahoo recently. Here's a nice positive Y announcement, albeit involving negativity (emphasis mine):
We’ve expanded the maximum number of account-level and ad group-level excluded keywords from 50 to 250, which should help you better target searches and block unwanted ones. .... Remember, excluded words can be set at the account level under the Administration tab and the ad group level in the ad group setting page.
-- from Yahoo Search Marketing Blog, Feb 1 2008
Thanks, Yahoo Search Team, for these new features!
Matchtypes and negatives play key roles in keeping your paid search ads away from less relevant search queries. Tuning your matchtypes and negatives let you cut PPC costs without sacrificing PPC sales.
RKG tip: invest time studying the actual search queries which trigger your highest-cost ads. Your logs often hold a rich trove of words to avoid. They can also suggest new concepts and ideas to add to your PPC campaigns.