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Yahoo announced last night it has acquired Koprol, an Indonesian mobile location-based service. With Koprol, which launched last year, users are able to see where their friends are and what they're doing in real-time. Like Foursquare here in the U.S., Koprol lets people check in when they arrive at a particular location and then share tips, reviews, photos or other messages with nearby users.

Is there a way to defeat spam? Late last week, the Yahoo Mail team shared news from an independent study that users of the Yahoo Mail receive significantly less spam messages in their email inbox than other competitive services.

We caught up with Vish Ramarao, anti-spam guru at Yahoo, to learn how the company was able to achieve these results and whether it is possible to outsmart spammers using more capable filters.

Google's announcement to offer cloud-based storage is in many respects an exciting development but it also illuminates the lock-in issue and why many an enterprise is reticent about adopting cloud computing.

We heard one of the clearest discussions on the issue today at the Webvisions conference in Portland by two senior engineers from Yahoo! and Facebook.

During my time in Boulder last week, one of the more interesting startups I was introduced to was Trada, a virtual marketplace for pay-per-click (PPC) advertising. Using Trada, advertisers and agencies looking to take advantage of search engine ad networks can crowdsource the development of keyword-based ads to the service's growing number of paid search optimizers. Previously, ads through Trada were only available on Google and Yahoo, but this morning, the startup has announced support for Bing and Microsoft adCenter.

Hadoop is gaining more commercial acceptance. We see a number of signs of its growing popularity. It became abundantly clear in a recent conversation we had with a Yahoo! executive who says the company is rebuilding its future on the distributed warehousing and analytics technology.

It's a similar track we are seeing with the larger consumer social networks and cloud computing providers. Facebook uses Hadoop to do deep social analytics which powers the ability to provide its established level of personal interaction. Windows Azure is adopting Hadoop.

Yahoo! says it is the world's biggest Hadoop supporter. We say that's undoubtedly correct. Yahoo! supports community developer events throughout the world. In February it supported the first Hadoop! event in India. In June, it will host the Hadoop Summit.

Email may be old fashioned, but it's still where we spend a lot of our time online. Today Google announced that its webmail service Gmail is becoming all the richer with the inclusion of support for sending Google Calendar invitations inside the email composition window.

In addition to being able to insert invitations, you can also cross reference your calendar availability with the availability of anyone included in your email thread that you have given permission to see the Google Calendar. It's not a perfect system, but it's pretty neat and it demonstrates the potential for building cool new features on top of our email inboxes.

According to the latest data from analytics firm Hitwise, Ask managed to grow an astonishing 21% last month (from 2.84% to 3.44%), while Microsoft's Bing actually lost 1%. After a long period of slow but steady decline, the total number of U.S. searches on Yahoo grew about 3% last month, while Google lost about 1% and fell under 70%. Alternative search engines only accounted for 1.93% of all U.S. searches.

Associated Press initially reported that three foreign journalists and one analyst have seen their email accounts hacked into today. The New York Times subsequently reported that there were "at least a dozen rights activists, academics and journalists who cover China," including the author Andrew Jacobs.

AP:

"They were greeted with messages saying, 'We've detected an issue with your account' and were told to contact Yahoo, they said Tuesday. Yahoo technicians told one of the four that his account had been hacked and restored his access, but it was not clear if the other instances were related."

We already knew that Facebook had usurped Yahoo's spot as the Web's second-most visited website in the U.S. in January, but today, Web analytics firm Compete also released its data for the rest of the top 50 sites in in the U.S. Unsurprisingly, most shopping sites registered a large drop in unique visitors since December, while tax services are seeing some of the highest month-to-month growth rates.