I received two emails this morning both stating the same thing (slightly different subject lines) - Yahoo will be cutting off ads at 75 characters. They had started this shortened descriptions some time ago but let you enter longer descriptions and they would only show the first 75 characters.

Seems now you will not have the option - all ads will use the 75 character limit.

"Beginning in late November 2007, if you have created short descriptions for your ads, those short descriptions will automatically be displayed on Yahoo! Search results (currently the short description will not always be displayed) but if you have not created a short description for a particular ad, the long description will be automatically cut off to fit within a 75 character limit," the emails stated.