We hope you're comfortable with a world that changes quickly, because on the internet not even the greatest successes can stay on top for long. Case in point: MySpace (launched in 2003), the first hugely successful social network, has been surpassed by six-month younger Facebook. Part of the reason for MySpace's past dominance was Facebook's policies about who could sign up and create a profile, but over the years Facebook has eased its restrictions. First only college students could join, then it was opened up to high school students, and then to everyone.

The boom for Facebook occurred mostly over the past year, with the latest record at just over 200 million unique visitors, or a fifth of the internet-using population. How many people do you know at this point who still exclusively use MySpace? Probably not that many, especially if you're outside of the United States; most of Facebook's growth occurred elsewhere. Even the Pope has joined up!

This isn't the only example of the rapidly turning tides of the internet; Twitter is now bigger than Digg, according to the BBC. Both are extremely popular with web professionals and geeks, and Digg (a site that promotes news stories based on popularity) was one of the biggest success stories of the past few years. Twitter (a blogging service that shares quick updates similar to Facebook status changes) grew 1,000% in the United Kingdom over the past year.

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