The New York Times has a commentary by John Battelle on how things are different this time:
First, this time the Web is ready for the dreams of both its innovators and its public. The first version of the Internet – call it Web 1.0 – was long on vision but short on execution and audience. The technology was rudimentary, precious few had broadband connections and starting a business that “scaled” – one that could deal with success and the traffic it brought – was extremely expensive.
The Web has since become a platform, and building new businesses on that platform is no longer a multimillion-dollar proposition. Most new Web businesses nowadays are started with less than half a million dollars, and it’s rare to find one that wants to use money from an initial public offering to get to profitability.