It is tough to get through a working week these days without handling at least a couple of invitations to join an online social network on Facebook or Hi5. There is little doubt that such social networks have seemingly emerged out of thin air to envelop our lives—and enrich it.

A new study by comScore, an Internet research firm, says that 580 million people used a social network site in June, 25% more than the number in June 2007. Most of the growth comes from places outside the US, where social networking first took off a few years ago.

Two out of every three Net users were busy networking online this June. So, it’s no wonder that companies and marketers are struggling to ride this huge wave of half a billion people.

But there are other ways that these networking sites will change the world. In places such as Egypt, young protesters have used these sites to organize protests against repressive regimes. The possibilities are huge—for both businesses and for civil society.