"How come you're not at All Things Digital?" I asked James Hong. The Hot or Not founder's distracted answer: "I'm too busy working on Facebook apps. It's the new internet." The excitement around Facebook's new 'platform' — a set of rules for third parties to build mini-sites within the fast-growing social network — isn't limited to Hong, or the bloggers who cluttered the news aggregators with breathless analysis. Slide's Keith Rabois, on his personal profile, wrote: "Keith is addicted to Facebook." Says another startup chief exec, in equal measures of enthusiasm and paranoia: ""I've been distracted with Facebook for about a week, trying to decide if my business is safe or not. If not then I should focus on Facebook. If safe then I should continue to focus on our site." All this commotion, over a bunch of widgets on the number two social network: what's gotten into the Silicon Valley koolaid? Here are four reasons some of tech's most sober entrepreneurs have suspended judgment.

1. Facebook is the alpha startup. First of all, entrepreneurs are in awe of Facebook's technical achievement. The social network, in its latest iteration, is snappy, uncluttered, and incredibly easy to use. The newsfeed feature — which shows in chronological order users' newest friends, photos, recommendations and states of mind — was controversial when it first launched. Now it's recognized as an interface innovation of genius. Facebook's partners — which include everyone from music recommendation service, iLike, to individual developers — assume that the social network will allow tighter and more interesting integration. Facebook, put simply, has an aura, in which other ventures want to bathe.

2. Idea epidemics. Silicon Valley's a close-knit place. Everybody goes to the same conferences, and communicates incessantly on instant messaging. Most of the people I quoted, above, know each other, amplifying eachother's enthusiasm. And buzz, when run through the echo chamber of blogs, can easily become overpowering din. On the day that Facebook's Mark Zuckerberg launched the F8 platform, Techmeme, the best aggregator of technology news, was overwhelmed by blog raves. The Silicon Valley community is now so highly networked that any half-decent idea quickly becomes an epidemic.

3. The Valley v. Myspace. Although Mark Zuckerberg founded Facebook when the 22-year-old was still at Harvard, he's now been embraced as part of the Silicon Valley establishment. While Myspace, upon which many Valley ventures depend for traffic, is down in Los Angeles, and owned by News Corporation, an East Coast media conglomerate. The Bay Area tech industry has always operated as some sort of confederation, contending against remote and monolithic giants, such as Microsoft, in the 1990s. Web startups such as Slide, needing ever-rising traffic to justify their valuations, are dependent on Myspace; but they hate that dependence; for little web apps, Myspace is the new Microsoft. Facebook, which promises they can set up shop within its gates, offers a less stifling alternative.

4. The new new thing. The tech industry thrives on novelty. Most new ventures have such tiny revenues that they need to project breathtaking growth rates in order to persuade investors, and themselves, that the effort is worthwhile. Since such miraculous trajectories only occur during a technological discontinuity, entrepreneurs are always quick to spot one, whether or not it's real. The biggest problem for budding moguls, and investors, is that all the new things — nanotechnology, rockets or clean technology, for instance — are way less compelling, financially, than the internet. Solution: declare, as James Hong has, a new internet. Which Facebook, conveniently, has provided.