I'm dubious of just handing these guys my browser history. Facebook et al use your social graph not just for personalisation but for advertising.
Also: filter bubbles.
the data collected from the history is not associated with the user account, only analysed; and the plugin/extension respects private/incognito mode, according to the privacy policy: https://lumi.do/about/privacy
So how are they supposed to personalise your content if they don't know who visited what?
great, another site wants to 'personalize' stuff based on what I 'like', so I can 'discover' stuff similar to what I looked for before.
btw hasn't the early StumbleUpon worked that way? browser extension + suggestions?
I loved Last.fm back in the day when all of our music was stored on the hard drive. Scrobbled an insane amount of data via foobar2000.
Recently discovered Rdio connects to last.fm so that data can flow from there too.