This week Facebook surpassed 500 million users, but that’s not the only reason the world’s largest social network is making headlines.

This post from O’Reilly Radar breaks down where Facebook’s half a billion users reside by region. Asia appears to be the fastest-rising region for Facebook users, currently sitting at 17% of the social network’s user base.

This week has been a big week for social media as the world’s most popular social network announced that it reached 500 million users. Salesforce.com is just as excited about it as anybody.

Barnes & Noble has introduced Nook for Android. This comes in the form of a free app that lets users read eBooks with customizable font styles. The company says this is the first Android eReader app that lets users share eBooks with friends.

The company also points out that this is the first eReader software to feature its new "NOOK-centric" branding. The app will soon be followed up with updated apps for the iPhone, iPad, and other devices.

The House Committee on Financial Services held a hearing Wednesday to discuss regulating Internet gambling in the U.S. and establish safeguards for licensed operators to put in place to protect against underage and problem gambling.

Consumers shouldn’t expect to be overwhelmed with search options if they decide to buy Windows Phone 7 devices.  A high-ranking Microsoft employee has revealed that there will be only one default search engine: Bing.

Facebook announced its 500 million user milestone yesterday, and along with that announced some other stats like how it gets over 100 billion hits per day. This was revealed in a post in which the company talked about how it scales with its massive growth.

Believe it or not, this is a good – or even great – day to be an eBay shareholder.  Although Google and Yahoo’s stocks basically fell off cliffs following iffy earnings reports earlier this week, eBay managed to publish some positive numbers this afternoon and has seen its stock jump in after-hours trading as a result.

Consumer Watchdog issued a press release saying that Google spent $1.34 million trying to influence federal lawmakers and regulators in the second quarter of 2010, a 41% increase over $950,000 in the same period a year ago.

Facebook isn’t the only one announcing impressive milestones today. Pandora announced at the New Music Seminar that it has 60 million registered users. That’s not exactly Facebook’s 500 million, but pretty impressive nonetheless.

It wasn’t that long ago that Pandora’s obituary was all but written, but things are looking bright for the company now.

Facebook of course announced today that it surpassed 500 million users, but the company has shared a few more stats today as well.

Facebook gets 100 billion hits per day. It has 50 billion photos. It has 2 trillion objects cached, with hundreds of millions of requests per second and has 130TB of logs every day. This is all according to a post in Facebook’s Engineering Notes.

Talk of free 30-day trials may not "wow" a lot of folks.  Some people, for example, will wonder whether a company won’t find an excuse not to take a product back, and other individuals realize just returning a product with a receipt can accomplish the same thing.  But local business owners should definitely take advantage of an opportunity to try Google Tags for a month.

If you’re ready to jump right in, here‘s a link to a signup page.  Enjoy.

Connecticut Attorney General Richard Blumenthal sent a letter today on behalf of 38 states to Google asking it if it had tested its Street View software before using it.

You may recall Facebook’s Gross National Happiness project, in which status updates throughout the social network are monitored for positive words to give an idea of how happy people are in general.

Facebook was expected to announce that it reached 500 million users this week, and sure enough, CEO Mark Zuckerberg announced it today.

Facebook has also launched a new app called Facebook Stories. This lets users share and read hundreds of stories about how they’ve used Facebook, categorized by themes and locations around the world.

Borders has launched a new "Textbook Marketplace" that allows users to buy and sell new and used textbooks.

The Marketplace features more than 1.4 million titles including a selection of used textbooks at a savings of up to 90 percent. Users can also earn cash via the site’s used textbook buyback option.

"College students spend nearly $1,000 each year on textbooks according to some estimates. That’s a sizable financial burden for students and families, especially in this challenging economic climate," said Borders CEO Mike Edwards.

Google has launched some improvements to its borders for over 60 countries and regions in Google Maps (coming to Google Earth soon).

It’s very rare that a major website launches any kind of redesign without any complaints from users. Google is no stranger to this itself, and it should come as no surprise that this week’s launch of the new Google Image Search has come with its own share of complaints (although I’d be surprised if the complaints outweighed the positive opinions).

Google Ventures has invested in a paid search marketing firm called Trada. Google Ventues has invested $5.75 million in Trada, along with Foundry Group, which previously invested $2.2 million in the company.

At SMX Advanced last month, Microsoft announced that Bing would redesign its Webmaster Tools this summer. The new version is now available.

Bing Webmaster Tools Senior Product Manager Anthony M. Garcia summarizes the changes:

MySpace and MTV.com are partnering to bring live streaming coverage of celebrities at Comic-Con.

Starting Thursday, July 22, daily live shows will be hosted by MTV Movies Editor Josh Horowitz and will stream on MySpace and MTV’s homepage. Users will be able to post comments and questions in real-time for a chance to have celebrities answer live.

Don’t be surprised if any security researchers you know start canceling meetings and spending more lunches at their computers.  Google’s set out to attract their attention by increasing the maximum reward for finding a Chrome bug to $3,113.70.

A couple weeks ago, Twitter unveiled its @earlybird account, which is designed to provide followers with exclusive deals from the company’s advertising partners and other businesses. Last week, the account got into full swing, as it tweeted its first deal from Disney.

However else Yahoo’s shareholders may feel about the company’s financial situation, they can perhaps take comfort in the idea that Carol Bartz won’t be wasting lots of money on champagne and confetti today.  Yahoo’s second quarter earnings report didn’t contain much news the CEO could celebrate.

You may recall last week when reports came out about some guy who claimed to own the majority of Facebook. Paul Ceglia claimed to own an 84% stake in the company, saying that CEO Mark Zuckerberg signed a contract with him in 2004.

The timing described didn’t appear to line up with common accounts of the founding of the company (such as the one in the book Accidental Billionaires – the basis for the upcoming David Fincher film The Social Network).