Facebook v. Power Ventures is a good illustration of the issues that arise under the CFAA.
The business background: Power Ventures observed that there are many social networking sites. A short list: There are a lot: Facebook, QQ, WeChat, QZone, Tumblr, Instagram, Twitter, Baidu Tieba, Skype, Viber, Sina Weibo and so on.
The large number of sites is a problem for individuals and businesses that have accounts on several sites and want to post the same message on all of them.
Power Ventures idea was to solve that problem. People could register on the Power Ventures site, provide their user names and passwords, and Power Ventures would post any message they sent to it on all the user's social networking sites.