An awesome anecdote from Philip Klein from the American Spectator blog:
OTTUMWA, Iowa--Last night, I attended a Mike Huckabee event at the Bridge View Center here and made the conservative estimate that he drew a crowd of 400 to 500 inside an auditorium that held 650. When I noticed that Mitt Romney had an event at the same place this afternoon, I looked forward to getting an apples to apples comparison. I showed up again today and walked into the auditorium where I had seen Huckabee the night before, only to find it empty. The Romney event "is in a much smaller room on the other side," I was told. Whereas the room where Huckabee spoke was the size of a large movie theater, for the Romney event I was directed to "Conference Room 1," where I counted about 100 people once the event started. With the race in Iowa currently a tossup, everything will hinge on turnout, which is incredibly hard to predict, but crowd size is probably the best measure we have.
To be sure, this is just one anecdote, and perhaps there are differences between Friday night and Saturday afternoon, or other varaibles that I'm not taking into account. Or perhaps Huckabee will follow the path of Howard Dean, who was unable to convert large crowds into turnout. But the dramatic difference in the crowd size is just one small example of the potential for grassroots enthusiasm to triumph over paid organization.