The problem is the bias inherent in the sample. The Joel on Software development community, Kiln mailing list, and StackOverflow all have something in common - they were started by Joel, and their initial userbase comes largely from followers of his blog.
I wonder what the results would've been had GitHub polled their userbase? Or if you asked a random sample of Googlers (hint: 100% would say "Perforce professionally", and then a good chunk would say "Git personally")? Or if Fortune magazine had had CIOs poll the individual employees of their firms (I bet you'd see a whole lot more Perforce, and a fair bit of "What's version control?")?
I wonder what the results would've been had GitHub polled their userbase? Or if you asked a random sample of Googlers (hint: 100% would say "Perforce professionally", and then a good chunk would say "Git personally")? Or if Fortune magazine had had CIOs poll the individual employees of their firms (I bet you'd see a whole lot more Perforce, and a fair bit of "What's version control?")?