Yahoo modified it's Web Services terms slightly… but only to the developer's advantage :-)

• Many of our services are no longer covered by restrictions preventing "commercial" use; we are giving you more specific guidance as to what's acceptable.
• Yahoo! Search APIs are now rate limited individually at 5K queries/day/api, giving you as many as 4 times the daily query allocation for your applications
• Yahoo! Maps APIs have their own Terms of Use – clarified exactly what kinds of applications are acceptable, and what uses you cannot make
• a new request form at http://developer.yahoo.com/register/ to have your application validated as being an acceptable use, to request additional queries, and to sign up to receive system status notices … sounds like a good thing for production use… this is where to go if you have usage questions or need more queries
• Significantly enhanced list of Frequently Asked Questions http://developer.yahoo.com/faq/

good news…