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Aside from the numerous comment systems (as mentioned, many of whom are very successful) the Facebook social plugin, which you use on this site, is also a widget. You could also make a case for social buttons. What's certainly true is the *word* widget has long been buried. I'd argue that "widgets" have simply evolved, and the companies you mentioned just had lousy products.
11 months, 2 weeks ago on Why the Smartest People in the Valley Were All Dead Wrong about Widgets