According to the Yahoo’s search marketing blog, short descriptions of 70 characters will be required by Yahoo! Search advertisers in May while the current 190-character description will relegate to an option only be shown in certain formats. Yahoo! cites performance as pre-empting the change, “Weâ€™ve found that ads written more concisely give users a better experience and perform better for advertisers. When users are exposed to higher quality search ads you, the advertiser, may attract more interested and enthusiastic potential customers.”
Whether or not that holds true for you, you will be able to exceed the 70 character limit but starting in June, paid search copy will be cut off near 70 characters (as needed to fit the most complete word). Long descriptions, apparently, will continue to be shown on some external distribution partner sites.
While on their Australian domain, I think we can assume this won’t remain (or be limited to use as) an Australian product. Yahoo! Alpha allows users to create their own search engines and serves as a response to Google Co-op and Microsoft’s Windows Live Macros.
This time, in playing catch up, Yahoo! has finally gone further, creating a customizable search service that allows users to leverage a variety of Yahoo! and 3rd party search tools. Wickipedia, Flickr, and YouTube results appear automatically and the engine can be customized to include results from virtually any source.