Take the example of Facebook. It was launched in two thousand four as a social network just for Harvard students.

VOA: special.2009.09.14

And so it’s not quite as useful as Facebook which is great for social reasons.

对于拓展社交圈的话，它不会比Facebook更实用。

便利的社交媒体 - SpeakingMax英语口语达人

net For those unfamiliar this is a website at courses.cs50.net and has the entire Harvard Course catalog in it and what it has at top left as you might see is definitely your Facebook login button.

还不熟悉的同学可以登录courses。cs50。,整个哈佛大学的课程目录都在上面,在这个网页的左上角,可以看到Facebook的登录链接键。

哈佛公开课 - 计算机科学课程节选

Now anyone can join. Facebook said it had over two hundred fifty million active users as of July.

VOA: special.2009.09.14

Facebook started as a site for college students to share interests and information.

VOA: special.2010.05.28

as in a friend you accepted on Facebook?

VOA: special.2009.09.14

The question has to be 'How do we maximize the value of the traffic that we're going to receive?'" For a lot of advertisers, internet advertising, social networking sites such as Twitter or Facebook, and internet searches on sites such as YouTube can be the answer.

VOA: standard.2010.01.27