Health 2.0, web-based apps and services for the healthcare sector, is a nascent but potentially huge market for web 2.0. As of now, many of these apps have an emphasis on communication, information sharing and community. These are relatively easy things to address using Web tools. However we're starting to see health 2.0 apps try to tackle the enormous inefficiencies in the healthcare system - check out our description of Carol.com below. Also, in the longer term, we will see the Web being used in medical diagnosis and practice.