In Activity Streams, verbs are their own objects, and the variety of actions that can be represented is limited only by the standard itself. Providers can also use verbs outside the standard, taking the chance that they'll eventually be incorporated, or that a downstream client could parse them anyway. Here's a list of the verbs incorporated in the Activity Streams standard so far:
A US study (http://pewinternet.org/Reports/2010/Social-Media-and-Young-Adults.aspx) has indicated that younger internet users are losing interest in blogging and switching to shorter and more mobile forms of communication. The number of 12 to 17-year-olds in the US who blog has halved to 14% since 2006, according to a survey for the Pew Internet and American Life Project.