With the power of JavaScript widgets, we've seen how it is possible to embed sophisticated mapping functionality on a site. There are plenty of other JavaScript widgets available that provide additional functionality.
Discussion and comment services can be used by embed this functionality on a site. All the "work" of the discussion / comments (authentication, storing, displaying, etc.) is handled by the third party. For example, comment functionality for WBUR and the Harvard Crimson use the service Disqus. Other examples include Livefyre and Intense Debate
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