Monday was the first day of Techcrunch50 at the San Francisco Design Center Concourse. 52 start-ups from a pool of over 1000 were chosen to demo their products over the conference’s three days. For each of the day's four sessions, four companies were given eight minutes each to demo their product. After every round, a panel of experts gathered to evaluate each product and give their input, especially on how to monetize a product. By the end of the day things had gotten more casual and experts were adopting an “American Idol” manner of interacting with presenters, probably under the influence of expert Yossi Vardi, a VC who would be at home on Car Talk. Among the start-ups that most interested the experts and audience were:

- Yammer, a “work-place Twitter,” was a big hit, not so surprising when you consider that half the people in the audience were tweeting as they watched the presentation.

- Blah Girls, a pop-culture site that is hosted by a trio of animated teenage girls. Unlike the other start-ups, monetization should not be a problem, as Ashton Kutcher has proven with “Punk’d” that he has the savvy and branding to succeed with his spin on something that already exists. (Watch our video)

- DotSpots, which allows in-text annotation of articles, embedding comments, videos, and photos.

The two themes Techcrunch50’s first day were social media and monetization. A third might be said to be celebrity, as some of the big names in tech – Arrington, Marisa Meyer, Jason Calacanis – spoke, and myspace CEO Chris Wolfe was a surprise guest.

Techcrunch50’s atmosphere is decidedly more Hollywood than your standard tech conference, with appearances from Ashton Kutcher and Buffy/Firefly creator Joss Whedon (Wednesday), and parties featuring DJ Samantha Ronson, probably best known as Lindsay Lohan’s girlfriend. Definitely a social media vibe. It’s not every tech conference where you can watch Kutcher in the lobby getting punk’d by his own phone.

Something that was confusing at first is that the conference badges make it look like all the speakers are wearing white suspenders, which is disorienting but homey, like all the presenters had just gotten back from an Amish commune.

Techcrunch50 continues Tuesday and Wednesday.

By Mark Alvarez