Doug wrote:
"I just got an email from ANSWER claiming 300,000."
like others i don't think the absolute numbers ultimately matter. but, for what it's worth, in another life i've had to do a bunch of different estimates on operational and process flows as well as network capacity limits. one way to estimate the numbers is to draw a figurative check point, estimate the flow through at any one moment in time, figure out an average flow cycle and then multiply by the total time.
applying that logic here's how i'd estimate the crowd:
at say 15th street & pennsylvania ave the street held what looked like 40 to 50 people wide, so use the average of 45. there were many stops, starts and flows just like any traffic jam. but let's again estimate that each row of people passed by this checkpoint at an average rate of one row per 3 seconds. that's 900 people per minute or 54,000 per hour. the march lasted at least 2.5 hours. by this crude (and probably silly) estimate that means approximately 135,000.