The Republicans should be worried if this is the future of campaign fundraising. Ezra Klein elaborates:
I don't actually think Barack Obama's remarkable advantage in small-donor fundraising is all that inexplicable. As a Dean Campaign alumn, I'm contractually required to believe that raising tens of millions from small donors is an internet-based phenomenon ... Obama's site gets way more traffic than Clinton's (and both get way more traffic than McCain's -- he's that little mustard colored line near the base of the graph). And with way more web traffic comes a way larger e-mail list, and with a way larger e-mail list comes more donors who eventually succumb to a fundraising appeal and donate $20, and when they do that, it becomes far more likely that they'll do it again, as now they're invested in the campaign. Add in that a pretty high percentage of Obama's voters are fervent backers, rather than soft supporters, and you have a recipe for some impressive fundraising.
Matt adds:
Obama beating Clinton this badly is pretty much expected -- it falls out from the differing demographics of their bases with Obama doing better among younger people, better educated people, and wealthier people, all webbier groups. John McCain's pathetic performance seems noteworthy -- is he just exclusively the candidate of the elderly?