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I've been seeing more useful utilities for Twitter crop up lately than for any other platform. This one is called TwitterSearch, and its goal is to allow you to find folks in your circle who have already signed up for Twitter (without forcing you to send all of them an invitation through the Twitter invite engine).
It's the perfect solution for the Twitter user that has a large circle of friends that are mostly tired of getting bacn'ed to death by all your social media invites.
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