We congratulate Hanson et al. (1) (Integrating 2.0 Health Education Preparation and Practice this issue) for highlighting important trends communications technology and how new channels can be used to reach audiences. The advent of 2.0 also provides the potential for exciting new teaching strategies if health educators can become proficient their use. The authors point out, rightly, that these tools are low cost and easy to use. However, the very features that make 2.0 so exciting also bring serious concerns about the unintended consequences that might arise. This brief discusses some of the issues that must be considered when deciding when and how to use these new technologies, beginning with a critical examination of the most oft-cited benefits of 2.0. Web 2.0 gives us new ways to reach people. Hanson et al. highlight the increasing use of 2.0 applications. However, research is lacking to show who is using these applications for health education and promotion. We also do not know about the extent and intensity of use. Many people who view blogs and wikis never post on them, and even fewer create their own or maintain them consistently. Therefore, we must be careful not to extrapolate from general use to use that is meaningful for health education. Web 2.0 is empowering. These tools enable users to self-organize around issues they find important and interesting. Hanson et al. suggest creating online communities and attracting users to them. However, doing this effectively probably requires an extension of our understanding of the theories related to community development, if not entirely new understandings. How do we ensure that health educators do not experiment on their constituencies with new technologies rather than use these new technologies as tools backed by established scientific methods? Further, health educators may lose the power of self-organizing and be seen as external to the community. Web 2.0 democratizes knowledge and lets users control the content. This promise is based on all the premises of media. The very freedom of people to generate their own groups and content can result barriers to effective health education. Some groups have even formed to support negative health behaviors and attitudes, such as pro-anorexia online communities. Besides the purposeful spreading of negative health behavior information, some incorrect information can be spread unwittingly if people believe falsehoods or rumors and share them. 2.0 applications may therefore prevent health educators from controlling health messages adequately. There is recognition now of a newly emerging issue--the persistence of information an environment that can be reached by anyone at any time. For example, whenever the Food and Drug Administration releases recommendations regarding food security, that information inevitably ends up on the web and is communicated extensively on many sites. Yet, if these recommendations change over time as a result of new science, the prior recommendations cannot be removed. Unlike books, which usually become inaccessible over time, information on the web persists, giving people old guidance based on science that is no longer sound. Web 2.0 engages target audiences better than traditional media. Consistent with other entertainment media, online materials have the potential to involve audiences more fully with health content and social support. But health educators should keep mind that, according to cyberculture studies, the virtual world has its own culture, and people operating within it behave differently than in real life. Perhaps most important, they often exhibit fewer inhibitions against certain mental health and health risk behaviors. (2) Web 2.0 gives us new ways to evaluate. Hanson et al. demonstrate how easily one can monitor traffic (hits) and where people go (click path) on 2.0 applications. …