Mounting an Online Posse
By KATIE HAFNER

FOR two years, Jason Eric Smith, a 21-year-old sophomore at the University of New Orleans, had been finding good deals on used Macintosh computers and then reselling them on eBay.

Until a week before Thanksgiving, Mr. Smith's small enterprise ran smoothly, yielding just enough to pay the rent. Then a sale went terribly awry, leaving him a victim of a buyer's fraud. And in his outrage he persuaded fellow Mac users to take up his cause, turning themselves into sleuths armed with the Internet's power and reach.