A computer program can be set to automatically donate to Dean at a predetermined time (like when he announces a "fundraiser" on the net) and the money is transferred to Dean from all those dummy credit card accounts. The accounts are then paid from the funds deposited by the donor.
Democrats do not donate small amounts over a long period of time to a primary candidate. I have two democrats in my family, and one (my union brother) NEVER donates, as he counts on the union to do so. The other, one of my sisters, donates only as the general election approaches, and she gives small amounts one time.
Democrats have NOT been able to count on small donors for a long time. Why does Dean suddenly have all these donors? I maintain that it is an elaborate fraud, and one which will remain hidden unless we get lucky.
I hope that some computer gurus are, even as we speak, having a look-see at the question you raise.
John / Billybob
Because he has, to put it brutally, excited all the marginalized freaks of the Democratic party that are unhappy with anyone who tries to become more centrist. They project onto him their vision of the ideal candidate (i.e. one that thinks just like they do) long enough to get out their credit cards (internet donations, remember).
The only person this crowd despises more than Bush is Clinton. He was the shining hope that tricked them with honeyed words and beguiling promises. One thing that Dean has that all the other candidates lack is a certain amount of credibility in his stated opinions. He's losing that daily, true, but we're talking about donations in the past, not future.