The reaction to the 2009 U.S. Preventive Services Task Force recommendations that women in their 40s did not need routine mammograms was swift and furious. Using email, social networking sites and electronic bulletin boards, breast cancer survivors vented their outrage. Researchers say the magnitude of the reaction heralded a new era in the online exchange of health information -- one that's faster, fiercer and more powerful than before. The reaction to the task force's recommendations "was a great illustration of how two worlds collide," said Kristin K. Barker, a sociologist at Oregon State University, and lead author of a new study. "On the one hand, you had the science that was saying mammography for women in their 40s might not be as effective as we thought, and on the other hand, you had the personal experiences of the women who believed they were saved by having a mammogram."