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iStalkr, which is currently in public beta, has an idea that's very similar to the premise of Ziki.
It's essentially a feed aggregator for all your social sites: Digg, Del.icio.us, Ma.gnolia, Flickr, Last.fm, Google Reader's Shared Items, Tumblr, Twitter and more. Others who follow those feeds becomes your "stalkrs".
It's a simple idea and the execution needs some work. What's more, this idea hasn't been massively successful in the past, despite attepts by Ziki, SuprGlu and others. That said, let's watch this space.