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1.
Hijacking a shared resource tag, such as a Twitter hashtag or Delicious category for personal gain or to dominate the conversation.
Our shared conference tag was great until all the advertisers starting tagjacking the conversation with sales pitches.

Brian Brushwood was totally tagjacking the live Twitter hashtag feed at the Digg party, and it really got out of hand.
by arlingtone April 15, 2010