While Q3 2009 data showed email on top for content-sharing, February 2010 information from social optimization platform Gigya points to Facebook as the Web’s top social sharing hub.

Almost one-half of article links, videos, photos and other content shared via Gigya’s widgets are posted to Facebook, with another 29% broadcast through tweets.

Social sharing widget AddThis also distributed the most content on Facebook (33%), followed by a long tail of other options. Similar results were posted in summer 2009 by the AddToAny sharing widget; Facebook, with 24% of shares, took the top spot.

In addition to sharing content with contacts, social site logins are often chosen as a method of user authentication on third-party sites. Facebook was No. 1 for this purpose as well, but usage was dependent on content type, indicating that Facebook users may be most concerned with sharing fun, entertaining content on the network.

The social giant’s 52% share of authentications on entertainment sites dropped to just 31% on news sites, where Google made a close second place showing with 30% of logins. Yahoo! also boosted its share to one-quarter of news site authentications.