An analysis of campaign finance records by The New York Times this week found nearly 3,000 donations to Mr. Obama, the Democratic nominee, from more than a dozen people with apparently fictitious donor information. The contributions represent a tiny fraction of the record $450 million Mr. Obama has raised. But the questionable donations — some donors were listed simply with gibberish for their names — raise concerns about whether the Obama campaign is adequately vetting its unprecedented flood of donors.