SSarah Lacy works at Yahoo. Sort of. As the anchor of Yahoo Finance's Tech Ticker show, Lacy is a contractor, an employment status which already makes her a second-class citizen on the Yahoo campus. But Yahoo's ostracism of its Web-video star goes further. She's not listed in Yahoo's electronic directory, and her badge doesn't admit her anywhere on campus. Jerry Yang, Yahoo's nervous-nelly CEO, seems afraid that the longtime Valley reporter might stumble across his secret layoff plans. What his ban has really accomplished: Obstructing floral deliveries.