We don't have the numbers for this past Friday, but if you check the
Unused Whitney Permits - 2007 thread, on the past three Fridays, there were an average of 6 unused overnight permits (or 54 used), and 21 unused dayhike permits (or 79 used). So if this past Friday was average, you should have seen about 130 hikers on the trail. Spread out over 11 miles, that is only a dozen in any one mile stretch, or maybe 25 an hour.
I think it would be interesting for someone to carefully count the number of people they meet in a day on the trail, and then ask others in the group afterwards to estimate how many they encountered. I am curious whether actual numbers and perceived numbers vary much.