If the Whitney Museum were a bar, the 2008 Biennial would be its happy hour. Social networking is of the essence at this biennial, a fraternal, anarchic gathering. Many of the artists know each other and work on collective, nonstudio-based projects — in addition, sometimes, to making their own objects.

But it is not a private drinking club — the public are welcome revelers, too. Anyone can sign up for the 24-hour dance marathon, attend the slumber party, or participate in the choreographed animal movement class for children and adults — all events staged as part of installations at the Park Avenue Armory, the biennial’s second venue. And there is even a bar — organized by exhibiting artist Eduardo Sarabia.

This is a boho biennial, and a neo-hippy ethos is reflected as much in the finished objects as it is in the leisure-hour activities of the many of the 81 artists on display.

Indeed, the thirtysomething curators Shamim Momin and Henriette Huldisch have populated the exhibit with self-consciously scrappy, ephemeral, loose-at-the-edges art in their search to define the zeitgeist. By all accounts, that process was more an amble than a scramble. The number of artists included this year, 81, is down from the 106 of the jumbled, sprawling 2006 edition of the 77-year-old institutional fixture. Of the artists selected, 43 work in New York and 29 in Los Angeles or the Bay Area. Of the few working elsewhere in America, three are in Miami.

In keeping with youthful cool, the prevailing mood of the biennial is of casual idealism. Much of the work is politically or ecologically engaged, but in place of grand statements, anger, or urgency, there is a sense that gentle subversion will aid the revolution more than barricades; that sweet silliness, rather than heavy ideology, is the Molotov cocktail of choice. Ms. Huldisch used Samuel Beckett’s notion of “lessness” to characterize the dissipatedness and ephemerality of the art selected. In harmony with the thesis of the New Museum’s inaugural “Unmonumental” show, Ms. Huldisch stresses the keyword of “local.” This is low-carbon-footprint art that is about little moves rather than big gestures. It favors recycled, or at least modest, materials, and minor efforts in transforming them. It embraces failure, not in a heavy old existentialist sense of radical doubt, but rather humorously and solipsistically: Think holy fool, not tortured genius.

The installation at the Whitney by the late Jason Rhoades, “Theareola,” with its scaffolds, office chairs, CDs, and accumulated personal detritus, epitomizes a scatter aesthetic. Decentered in a carefree-cum-careless way, it has the typically Californian avant garde fusion of slightness and abjection. Fellow Californian Charles Long opts for a more rustic assemblage that recalls Anselm Kiefer and Cy Twombly but minus the bombast of these big-ego masters. Rodney McMillian, another Angeleno, has a monumental scale but suitably unmonumental attitude toward materials and finish in a goofy untitled work of 2007 that involves disheveled sheets of vinyl.

New Yorker Phoebe Washburn is more overtly ecological in medium and message alike, with her ecosystem sculptural installation, “While Enhancing a Diminishing Deep Down Thirst, the Juice Broke Loose (the Birth of a Soda Shop)” (2008). Rachel Harrison’s sculptures are low-octane riffs on Robert Rauschenberg’s combines. Rashawn Griffin’s suspended assemblages in fabrics and blankets gently mock 1970s pattern abstraction and New Image painting. Joe Bradley’s schematically figural shaped canvases, which stretch synthetic polymer on canvas, achieve the “intentional shoddiness” to which the artist reportedly aspires. They gently acknowledge the figural minimalism of Joel Shapiro and the abstraction of Ellsworth Kelly, though they eschew any of the tightness and rigor of these artists.

Art that takes its charge from mocking other art, though, is generally absent from this show, despite the inclusion of a veteran 1980s appropriation artist, Sherrie Levine. Instead, it is simply the lack of formal cohesion that suffices as the deflationary, antiheroic, anti-Art-with-a-big-A statement for most of these artists. The cute, at once neat and flimsy personalism of Frances Stark’s collages fit this bill, as do the exuberantly ditsy tableaux of Rita Ackermann that combine illustration and collage. Like Karen Kilimnik, whose faux-rococo paintings are installed nearby, Ms. Ackermann represents a fin de siècle that insists the world is to end not with a bang, but a whimper.

Ms. Kilimnik, though, does not enjoy much painterly company. Of the 81 artists, maybe five — if you adopt a liberal definition — are painters. Why? It is impossible to believe that the laissez-faire young curators seriously believe that painting is dead (yet again). More likely it is because painters do not make good networkers; assemblages in flimsy materials are more conducive to socializing, collaborative-minded artists.

But even in a biennial in which attitude trumps form, pockets of formal resistance are to be found. Jedediah Caesar’s head-cheese-like sculptures that suspend found scraps of material in colored resin were a discovery for this critic. These forms are rich and strong in a show whose organizers willfully eschew such aesthetic virtues.

Until June 1 at the Whitney (945 Madison Ave. at 75th Street, 1-800-WHITNEY) and the Park Ave. Armory (643 Park Avenue at 67th Street, 212-616-3930).