The real kicker here is that he's giving people incentive to group together all their profiles across the web, allowing Duck Duck Go to search people better than anyone else.

That's genius!

This gives me a bit too much foresight credit. Honestly, I got the idea for these widgets after seeing one too many comments like this one: http://news.ycombinator.com/item?id=379936. I agree with that thread that your YC karma isn't too useful on other sites, but then I realized it would be useful to display on your own sites.

So I got to building it... I quickly realized that there is karma on other sites, and it might be cool to aggregate. Then I realized I could possibly generate some new Duck Duck Go users this way. Then I realized (by someone indirectly pointing it out to me), that there are SEO implications when deploying widgets.

But I didn't think (until your comment) about improving search by aggregating profile information :). Just to be clear wrt privacy, we're not currently storing any IP info or the aggregate usernames in the DB, and have no plans to do so: http://duckduckgo.com/privacy.html

Such karma across many platforms and that is verified by trusted contacts(your friends) will prove in general to be extremely powerful for semantic/social services!

For example an idea of mine is to create a Rotten Tomatoes meets Twitter. Instead of indexing/compiling trusted press/bloggers I want a web-service/site that reads, understands and compiles all the reviews on Twitter about each movie. Right now I have to search tons and tons of Twitter search pages, as opposed to a web-service doing this automatically and presenting it in a simple UI. This same idea can be applied to tons of topics..restuarants, hotels, etc, etc....

One issue with this idea is it can be gamed easily, but not if this service only reads, understands and compiles from trusted/verified sources (karma being a good way to achieve this).

Might be abstract, but 1st time writing this idea/thought out!

Beautiful link bait. Seriously, it's a really clever idea. Fortunately/unfortunately Google frowns on link bait unrelated to the core business of your site: http://www.seomoz.org/blog/widgetbait-gone-wild so this is definitely somewhere in the gray SEO area.

You know, what I would love and use right away on some of my blogs is a similar widget but that allows me to include voting badges - particularly one that uses that script that came out a while ago to detect whether the user is logged in those voting sites and displays them only if they are.

That would be one heckuva handy widget!... does it exist anywhere?